Zelda BOTW was obviously delayed for strategic reasons to launch with Switch. Rumours pointed Mario Odyssey was done a while back and even ready for Switch launch. Mario Vs Rabbids apparently was a Wii U title and moved to Switch. These are just examples we hear about. Also alot of Nintendo games are polished on release, so it would surprise me if these games are done and put on hold for a good time to release. Hell Retro game could be ready last year and they decide to hold off for this year. Or even it's ready for this year but they saving it for 2019. Who knows how Nintendo's pipeline is.
Yeah, going to need some sources for those.
BotW most likely is true, but really sceptic about the others.