Unfortunately I cannot off the cuff cite a source (if I find one I'll add a link to it, though). I can tell you the context in which I came across this. A couple of months ago there was a story that Adobe were "sabotaging" HTML5 - in reality it was Larry Masinter, Adobe's representative in the HTML WG, arguing that the canvas API falls outside of the charter of the working group. In one of the blogposts in defense of Adobe's position the author quoted similar objections that Apple and Microsoft have made regarding <audio> and <video> codec support when HTML5 was still in transition from WHATWG to W3C.

Apple have most certainly expressed concerns about Theora's performance and patent situation and I'm sure they still have them. However, those concerns were pertinent when HTML5 was being developed by WHATWG, because WHATWG are not limiting the scope of any work they do. That's not the case with W3C's HTML WG.