Riven killing Yasuo's master no longer canon?

No tl;dr for you, sorry.

EDIT: As many have pointed out, it was never officially canon, merely speculation. My mistake. However, my argument that Riven is extremely unlikely to be the true killer is not impacted by this.

For a long time it's been canon, or at least considered canon by a lot of people, that Riven is the true murderer of Yasuo's master and the reason he is wrongly accused of his murder. Basis for this hypothesis were special interactions Yasuo has with Riven in-game, suggesting that Riven is capable of using a technique similar to his own wind-technique. Yasuo was the only suspect for the murder of his master, since he was believed to be the only person capable of using this wind technique.

In-game quotes:

Wait, that technique... huh.

Huh, three swift strikes...

Another wind blade?

Who taught you that?

However, with biography updates to Riven and Yasuo it is highly unlikely for Riven to be the killer.

Here are the events in chronological order: From Riven's biography:

As this new war dragged on, it became clear that Ionia would not kneel. Riven’s unit was assigned to escort another warband making its way through the embattled province of Navori. The warband’s leader, Emystan, had employed a Zaunite alchymist, eager to test a new kind of weapon. Across countless campaigns, Riven would gladly have given her life for Noxus, but now she saw something awry in these other soldiers—something that made her deeply uncomfortable. The fragile amphorae they carried on their wagons had no purpose on any battlefield she could imagine...

From Yasuo's biography:

When word of the Noxian invasion reached the school, some were inspired by the great stand that had been taken at the Placidium of Navori, and soon the village was bled of the able bodied. Yasuo longed to add his sword to the cause, but even as his classmates and brother left to fight, he was ordered to remain and protect the elders.

The invasion became a war. Finally, one rain-slicked night, the drums of a Noxian march could be heard in the next valley over. Yasuo abandoned his post, foolishly believing he could turn the tide.

From Riven's biography:

The two warbands met increasingly fierce resistance, as if even the land itself sought to defy them. During a heavy rain storm, with mud pouring down the hillsides, Riven and her warriors were stranded with their deadly cargo—and it was then that the Ionian fighters revealed themselves. Seeing the danger, Riven called to Emystan for support.

The only answer she received was a flaming arrow, fired out from the ridgeline, and Riven understood this was no longer a war to expand the borders of Noxus. It was to be a complete annihilation of the enemy, no matter the cost.

The wagon was hit straight on. Instinctively, Riven drew her sword, but it was too late to protect anyone but herself. Chemical fire burst from the ruptured containers, and screams filled the night—both Ionian and Noxian falling victim to an agonizing, gruesome death. Shielded from the scorching, poisonous mists by the magic of her blade, she bore unwilling witness to scenes of horror and betrayal that would haunt her forever.

For Riven, memories of the time that followed come only in fragments, and nightmares. She bound her wounds. She mourned the dead. But, most of all, she came to hate the sword that saved her life. The words carved into its surface mocked her, reminding her of all she had lost. She would find a way to break it, severing her last tie to Noxus, before the dawn.

From Yasuo's biography:

But he found no battle—only a raw grave for hundreds of Noxian and Ionian corpses. Something terrible and unnatural had happened here, something that no single blade could have stopped. The land itself seemed tainted by it.

From Riven's biography:

But when the blade was finally shattered, still she found no peace.

Stripped of the faith and conviction that had bolstered her entire life, Riven now wanders Ionia’s battle scarred landscape in self-imposed exile, seeking atonement from those who cannot forgive: the land, the dead, and herself.

From Yasuo's biography:

Sobered, Yasuo returned to the school the next day, only to be surrounded by the remaining students, their swords drawn. Elder Souma was dead, and Yasuo found himself accused not only of dereliction, but of murder. He realized the true killer would go unpunished if he did not act quickly, so he fought his way free, though he knew this would all but confirm his apparent guilt.

The only possibilities for Riven to still be the killer are:

1. Riven killed Yasuo's master after the explosion, but before Yasuo returned to his village. Since she has no clear memories of that time it could be she doesn't know herself. However, she lacks a motive; the wake-up call (or rather explosion) already happened.
2. Riven killed Yasuo's master after Yasuo left, but before the explosion. She abandoned her escort job to kill Yasuo's master and Usain-Bolted back to witness the explosion, highly unlikely but hilarious to imagine
3. The explosion Riven witnessed is not the same Yasuo found the aftermath of. Although it sounds likely there are a few points contradicting it. The events in Yasuo's biography had to take place before those in Riven's biography. However, Riven's bio doesn't mention her warband fighting before being assigned the escort job.(It does, my mistake) Also, it specifically says the warband they were escorting had employed a Zaunite alchymist, eager to test a NEW kind of weapon, making it impossible for the same weapon to have been used before.

Anyway, what do you think? Is there another explanation? Is there anything I missed? Let everyone know in the comments.

Sources: https://universe.leagueoflegends.com/en_GB/story/champion/yasuo/ https://universe.leagueoflegends.com/en_GB/story/champion/riven/ http://leagueoflegends.wikia.com/wiki/Yasuo/Quotes