I dont think Nintendo banned them, I think a lot of them are in the same boat as Nintendo didnt want to talk about games and marketing stuff for Switch during the holidays.
remember Lego City got announced for Switch
But games like Fifa, Skyrim remaster and NBA 2K17 are out now, if they announce them now they think they will lose holiday sells for people waiting on the Switch version.
Obvious exclusives they def dont want to announce early becouse you want the buzz to start with the system announcement.
Oh, come on. Skyrim and NBA 2k17 have been in announcement video. If the third parties had some issue related to holiday sales they wouldn't have allowed them to be in that video. FIFA is selling constantly well all around the year, again not a big issue if another platform comes out in March.
It would have laughable if Lego City would have been announced for PS4 and Xbone and not for Switch. It would have created a lot of negativity instead. That's why I think they were allowed to announce it.