I agree that hearing and vision impairments are primarily health/safety issues, and that it’s on-topic to track them in the iOS Health app (vision isn’t, though). Frequency of variance isn’t really a gating criterion for inclusion in the app.
I can’t think of a good reason to exclude Health from iPadOS, as that’s also a good platform to look at the metrics, even if it doesn’t access all of the necessary Apple sensors to record the data. Also, much of that data can be hand-entered.
By the way, I looked at CPU usage on my iPhone 12 Pro (using CPU-x) while running the Music app, with and without Headphone Accommodations for Media. I didn’t perceive any difference there in utilization, so I suspect this isn’t an issue of battery/CPU load for the Apple Watch.
So far, my perception of audiogram-accommodated Transparency Mode and Media are similar; I tested the same song from the Music app in iOS and in the Apple Music app for Windows (there’s a preview available, streams 256 kb AAC) with JBL 305p MkII monitors in a near-field listening position, and the perceived audibility differences with and without Accommodations were pretty close. Are the Media Accommodations being applied by the source or the sink?
That said, my Widex Moments in Music mode sound better than APP2 Transparency, to a point; the Moment BTE mics are shadowed by my pinnae, so near-field treble response is more muted than in APP2 Transparency.
Another notable thing is that iOS uses 3D scans of the user’s pinnae for use in their spatial audio algorithms, and has pinna-located mics, while the Moment “digital pinna” algorithm seems to be user-invariant, and the RIC version doesn’t have the pinna-located mic advantage. +1 for APP2 Transparency with respect to sound location.
One thing to note: Transparency Accommodation often has to be manually toggled on/off/on to actually be applied, when going from Media streaming from the iPhone or other device. It’s a nuisance, and may also lead users to perceive that Transparency Accommodation doesn’t work.