Well, not to be an apologist, and I don't really have strong evidence to back this up, but we pass along a lot of videos from third parties to display at events, in lobbies, etc. in a variety of A/V systems (from smart to dumb) and the video plays/audio doesn't scenario tends to include 44.1 audio. Not enough that it's standard practice to resample and it certainly may be a codec/wrapper over sample-rate issue, but I'm bringing it up as it may be related here. Force a 48 so likely to play audio in most video system scenarios at a sacrifice of audio bit perfection. Video not a concern for Airport Express so no 48 force there. Who knows the motivation, but common video scenarios tend to be doing a lot more up/down-sampling than most audio scenarios. Or that's my theory.
On the Apple TV overall front, gave as a birthday present and with weekends firmware update including iTunes Radio, it seems a great device for a retired couple. Not knocking Pandora/Roku/GoogleTV/Squeezebox/Audioengine D2/etc. as there are several ways to do similar, but for them with an iPad and iPhone already in the house (so some controlling the Apple TV from iOS and some beaming from iOS), it's kinda an amazing thing to witness the speed they ramped up to the device. From Netflix to YouTube to recent trip and their lovely granddaughter photos as screensavers to the Frank Sinatra and Eva Cassidy/Diana Krall iTunes Radio stations, the house came alive.