That whole “100th episode” to be spring premiere is just for marketing, remember when 511 was slated to be the spring premiere, that was supposed to be the “100th episode”, then suddenly they got another episodes in 5A and Smash the Mirror became one episode again and season 4 suddenly has 22 episodes (after Adam said otherwise on both numerous time), that is just another instance of him bullshitting his fans according to what suits him, regardless if it doesn’t mathematically make sense.
I really can’t blame Adam for trying to market the 100th episode. If that means changing around the episode numbers, then whatever. I don’t see why fans would care much about that. I certainly don’t care at all. Bullshitting his fans seems a little aggressive.
P.S: notice that abc has never promoted 512 as the 100th episode so far and that’s because it doesn’t align with how they numbered the episodes.
I still expect that when we get the first promo for the back half here, they will mention it is the 100th episode. But maybe not.