MPT Switch was originally supposed to launch in February 2019; but I'm guessing that it was pushed back when Yoshi's Crafted World went through development hell, got delayed and messed up Nintendo's internal schedule...
Likewise, NSMBUdx was supposed to come out much earlier in 2018 and was finished a LONG time ago (I heard about it all the way back in September 2017!); so that delay was also probably a result of YCW...
What I really want to know though, is what the hell has been going on with Retro!? They had TWO projects that were supposed to have been released by now! (One being a joint project with NST and the other being one on their own...)
This reads like you just took a bunch of rumors and insider information over the years as fact without verifying whether or not it's true.