I did see some Sci-fi when I checked on Friday for my window (12/4-12/13). Granted, it was only for slots of 1 (solo diner here), and I didn't see alot.
Also, Coral Reef slots did start appearing much later in the day for me, weirdly enough, just not in those first few hours. And I was toggling between the app on my phone as well as the website on my pc, and switching between picking lunch/dinner and specific times to get all possibilities as some dis-ers had suggested who noticed getting different things opening up when you did that.
What's funny is you end up getting so disgusted about what you can't get, that you end up realizing "Oh, well, it's Disney, I can really eat in so many different places and be happy" (at least I can), and you just pick something else and are happy with it.
Like, I do really want to eat at Rose and Crown but it's not the end of the world if I don't, and in my case I have eaten there before quite a few times, and in terms of the food, I can always get the fish and chips from the outdoor kiosk right by there or if I really want a sorta similar experience, I can also visit Disney Springs Raglan Road (which I enjoy very much, too).
So, you do force yourself to adjust. After you feel like it's the end of the world LOL.
And I do know that even like the week of that I'm in Disney, I always see slots opening up for these places, so literally between now and during my trip, I know I will be able to make changes if I really want to. It's frustrating because as some of you have said, we do like to get things set in stone at the 180 mark but this sorta thing has happened before, and usu sally I can always make changes and switch things up in the 6 month lead up. It's hard to be patient LOL.