I kind of already guessed that the DLC is Switch exclusive when not only did Nintendo revealed that their Direct is Switch-exclusive, but the 3DS version did not get a mention at all. I kind of felt that the 3DS version is the version that got the raw end of the deal, because some of its levels are compromised (some have different objectives from the Wii U version) and now DLC is not made for it. At least the Wii U version released earlier and had the 3D World levels, and the Switch is the ultimate version. I imagine if Captain Toad were to get a re-release this year, there will not be a 3DS version at all. I suppose 3D is the best reason to get the 3DS version at this point.
I played it a while ago. The new levels like Goomba Galleon are fantastic, and so are most of the remixes, but the Boo-Spotting stages are real bad. They drag on, they're repetitive, and even worse, the Shy Guy Heights one has 2 Toads in areas that are clearly made for one player, so it just feels cramped and horrible. I don't wanna spoil but they did make a fun version of arguably one of the worst stages in the franchise, so thats an acheivement I guess.