Everyone releases albums partway through their tours now, usually because tours have to be planned far in advance and are expensive and hard to reschedule. the artist usually plans to finish the album earlier but haven't completed it (along with necessary videos) in time, so they complete actual recording (and videos) right before the tour, drop the video/single, start touring, then the mixing/mastering of the rest of the songs (which the artist usually isn't doing themselves, so they can tour during that) takes longer and finally the physical edition (if applicable) must be created, and that means the album might drop digitally halfway through the tour and the physical version might not be available until after the tour.

is this ideal? maybe not. but it doesn't seem to hurt artists or fans terribly. Grimes had success with this method last year. fans with tickets get to experience songs that will later become hits or classics, before anyone else knows the songs. artists get more time to work on the music. and while sales might take a minor hit (the album might sell more if you could have it available before the shows and sell it at the merch table) the ongoing tour will also amp up interest in the album when it does become available, and reviews of the shows function as advance publicity.

the downside of this situation is that if you are an artist and you haven't even released the album before the tour starts, you were probably late enough that even a single or track listing or album title or press release didn't get released until after you already sold tickets yo those shows, so you definitely haven't given potential ticket buyers a clear idea what kind of music would be played. with acts as popular and fashionable as radiohead- or even grimes- this isn't an issue, because they have enough super loyal fans to sell out shows even when nobody has any idea what kind of music they will play (and even... especially because nobody has any idea and everyone is eager to be first to hear their new style). however, if you are a more ordinary musical act not known for changing your sound in interesting ways, the main variation between your albums may just be in terms of quality (i.e. some of the periods in your career were better musically than others, but the basic style was the same) and in that case your fans may not be willing to pay for advance tickets to a tour featuring new songs they don't yet know are any good.

But provided you can get away with selling out a tour while giving no information about your upcoming album (which Radiohead has already gotten away with, and then some, since they actually sold out faster than ever before, while providing less information) there is no reason not to wait to release the album, if you need to, since those fans already bought tickets, and if anything, it might be more confusing if you reveal before the tour that your new album is in fact, in some style they may hate. Rather, if you wait and release the new material first in its live versions, mixed with older songs, you will be more likely to have your new musical path followed by your fans. Radiohead had success with this method with Kid A (they toured the already-finished new songs for months before releasing it) and Grimes also last year had this kind of success with Art Angels.