This decision really surprised me, actually, a tie-in app seems like a fantastic promotional tool if you allow fans to 'unlock' things in it by talking about the album and such, but that'd only really work pre-release. I'm sure a post-release app will still be interesting, but it could have given fans something to engage with while they wait for the album, too - missed opportunity, in my opinion. There'll surely be a web-based version, too, they wouldn't limit something so potentially huge to just Android/iOS users.