"Akasha kills Enkil in the books"
Yes, but in the show Marius says that when Enkil burned, so did most of the vampire population and that's why there were so few of them in the 20th century. So the twitter poster was speculating that the reason the show did this is to explain the absence of several TVC characters when it comes time to battle Akasha, since they probably won't have the time or budget to include everyone. Basically, they're saying that characters like Pandora or Santino may have already died when Enkil did
Pandora and Santino were both a lot older than Armand, and Armand is still there as well.
Whether they will include everyone there is another matter, but using that event to explain any possible absence would not match with the characters, and if the show has been very careful with, it is with the power levels and ages etc of characters. Despite their changes to the lore.