It's worth mentioning that Mary Skelter 2 comes with the first game, if you weren't aware.
I'd assume they picked it up and went to start with the Switch port of the first game.
Basically there are 3 different games so to say.
Mary Skelter, Mary Skelter 2 and Mary Skelter (remake)
Mary Skelter is the original game, Mary Skelter 2 is the sequel of sorts, then there's the Mary Skelter remake, which is the one bundled in the other systems, that version should be played after Mary Skelter 1 and Mary Skelter 2, it's basically the first game with content for the second game and a sort of true ending to the previous two games.
As far as I know, the remake should have been locked until people beat Mary Skelter 2.