While this feature mightn't be reinstated, I'm not of the opinion that its been intentionally removed. Remember its the OS we've updated and not the app.
Unless they've since included a blacklist of apps which are denied rotate capabilities I see this as being a simple API change which has broken functionality. Why that hasn't affected other developers I don't know, although I guess Apple may have used an otherwise undocumented API. It would be ironic if they've fallen foul of their own policy of vehemently dissallowing the use of undocumented calls.
Anyway, that's my spin on things. Eitherway I'm equally as annoyed as you guys, my perfect[feeling] audio setup has been left in tatters!! Well, that's how it feels anyway 😉