Why was Tahm Kench removed as Veigar's ally? (And another thing)

I don't know if this has been brought to light (or if anyone really noticed honestly) but the removal of Tahm as an ally of Veigar kind of...stings in a sense.

We know that, or at least are told, that ol' Fish lips visits all Yordles at one point of their lives or another, and given Veigar's backstory we'd be inclined to believe that Tahm was the one who offered Veigar a way out of prison (which makes a lot of sense both thematically and story wise). But now he's gone, kaput, vanished. On Tahm's own page, he has every single Yordle (and Fizz) as his rivals, all but Veigar who, as you've shown us before, would've accepted a bargain from the demon, which would (probably) add him to Tahm's ally list, or at the very least some sort of acquaintance.

But I don't know if Tahm's absence is just an honest mistake, or if the Lore Team is planning something for Veigar but at least for the time being, having Tahm as an ally than Lulu as a friend. While I'm blithering I might as well add another gripe.

Now I'm probably in the extreme minority here, but I honestly don't think that Veigar and Lulu would be friends, or even know each other really. Yes I'm well aware of the the old 'Misadventures of Lulu and Veigar' which was the driving factor of making the two official friends. But I can't help but be bothered by the fact that a sadistic, maniacal and twisted warlock would become friends with bubbly, energetic and mischievous...trickster? As cute as the shipping of the two is, with what we're given in their bios and ingame lines, them being friends (or even running into one another) seems highly unlikely.

All this being said, I could very well be complaining about nothing if Riot intends changing Veigar's backstory, or creating a situation where he and Lulu meet and he doesn't blow her up out of annoyance.

TL;DR Why Veigar and Tahm allies no more, and why are he and Lulu considered friends?