Yeah, this also took me a minute to figure out, but then I realized that if you look close enough, you can piece together that it is multiple splitting, and not multiple players. I must have searched the options in the game forever before realizing this.
And I totally agree, this is the BEST blackjack app I have played even at the single player limitation. It's supposed to be a Blackjack trainer, though, so it makes sense, but would love to see an option to add another player or two in a future release. Nothing like trying to card count your cards and everyone elses as well.