As you can see i scored a firstblood midlane yet the /remake worked for the enemy team. My guess is that the yes/no promp was being already on but people waited to choose and after first blood everyone picked yes.
ModWulf Helhammer1 votesIt's if the first blood is on the AFK player, before they AFKed
Setho Ao1 votesFirst blood was on the midlaner, who was not afk.
Zombiemaster1 votesRiot made a few adjustments since they first announced the remake system. First blood will only prevent a remake from happening if it happens before someone leaves. If it happened after someone has already left, then a remake will not be prevented.