We don’t know for sure if there is going to be 23 episodes for season. That information was suspect. That was amidst the confusing discussions about which episode would be the finale of 5A. There may be, but there might not be.
Season 5B was always planned as 12 episodes, while 5A was originally planned as 10 episodes until “The Bear King” was added as an episode. “The Bear King” being added didn’t suddenly make 5B 11 episodes instead. Here’s confirmation from both Adam and Jane, regarding 5B’s count:
@DigiRanger1994 no — right now it's 23
— Adam Horowitz (@AdamHorowitzLA) October 28, 2015
@LinLove95 @SwanQueenSwen there are 12 more eps scheduled for season 5. We're not even halfway thru season
— Adam Horowitz (@AdamHorowitzLA) December 10, 2015
@TheMatthewPaul @Betsypaige24 yep
— Adam Horowitz (@AdamHorowitzLA) December 10, 2015
@TheMatthewPaul Yes
— Jane Espenson (@JaneEspenson) November 15, 2015
Also, here’s a quote from a Variety article:
Horowitz: When we were asked to do the additional episode, it wasn’t part of the initial plan to make it a two-hour story, but what we did do is, we found what we hope is a really engaging story for both of the episodes — and there is a connective tissue between them, but they tell two separate stories. But one pushes right into the other one and kind of takes a left turn a little bit, but we think it’s a lot of fun.
Source: http://variety.com/2015/tv/news/once-upon-a-time-hades-100th-episode-emma-saves-hook-1201640947/