I suspect that this app uses Apples's leaked key for airplay encryption. In that case I would understand the rejection. I can't wait for the official explanation.
Funny how nobody else seems to notice this. That key is there for a reason, and one of those reasons apparently is anti-competitive behavior.
Keys and other mechanisms like it are not usually used to increase customer service but to increase vendor lock-in and control of those users. It's all about creating a captive audience.
It is part of the DRM scheme. DRM requires end-to-end encryption to be effective. In this case it has nothing to do with a vendor lock-in. Using DRM is part of the deal with media partners and not Apple's decision.
What Gruber actually said about this is, "I can’t imagine what Apple would object to with this app, or why they wouldn’t provide Rogue Amoeba with a precise explanation before removing the app."
Although I imagine if it was some company he didn't see favorably, he would probably go for your explanation rather than the one he actually posted for this.
I just realized that Rogue Amoeba isn't just a random company making iOS and Mac apps. They aren't even just a random company that Gruber likes. Rogue Amoeba is a past sponsor of Daring Fireball, including being the debut sponsor of the Daring Fireball RSS feed [1].
Given that, I'd be surprised if he'd said anything else. That doesn't mean what Gruber said here is wrong (I don't think it is), but that is important context nevertheless.