I get the feeling they know there's 0 way for there to be a season 2 at this point, so they're trying to have their cake and eat it by putting some of the series as a manga special on Youtube, while using the anime to rush to the end of the Shiho arc. Which just doesn't work in my opinion, as the anime feels like a rushed mess that ultimately doesn't do justice to any of the material / any of the couples. Especially with YoriHima being thrown under the bus by the anime.
It's a typical manga pusher product with lowest possible budget, regardless how enthusiastic staff and performers are. You stuff in as much of the story in as possible, so you can get more people trapped by the manga continuation, and hope for the best in terms of sales boost.
Pushers almost never get a second season or full adaptation.
I think it varies because there's a fair amount of anime that adapt what they can of the source material. Where it's an okay or even good but incomplete adaption. In my experience this level of rushing a series isn't very common, combined with all the various other problems. This and Unnamed Memory (as I was discussing with DrJamesFox previously) are I think the biggest rush jobs on anime this season, and maybe even this year so far.
Part of my issue is this doesn't even sell people on wanting to buy the manga from what I've seen. If this adapted what it could and then left on the note of to see the conclusion of Shiho's arc buy the manga!, I would have been fine with that as long as it handled the material it did adapt properly. The manner in which the anime butchered it's adaption of the manga is completely crazy to me, and frankly bizarre even when comparing it to other adaptions with issues. I also say they realized there was 0 chance of another season because of how much the behind the scenes sound like a complete mess, again more so than usual.
This whole situation is also interesting to me in contrast, because Yagakimi's anime adapted what it could, didn't completely rush it, and even though the season ends in a somewhat awkward place it's still a generally beloved adaption. All people really want with it is a season 2 from what I know. With Whispering I think we could have been in a similar spot with the adaption, but sadly instead of a season 2 we need a complete adaption reboot.