"Soundtrack remastered in 5.1" was Warner's standard boilerplate for years durring the snapper era. They even used it on films like Batman Returns and Under Seige that were 5.1 in the first place.
I would not be surprised if The Original Exoricist, III, and this upcoming sequel thing are the only Exorcists to ever make it to 4k anyway. II would have to be scanned again (for little financial gain since everybody hates II), and both The Beginning and Dominion were finished in 2k anyway (or...
Shout! only has Exorcist II and III (which they're licensing from Warner and Morgan Creek respectively). Beginning and Dominion are currently with nobody actually.