At the very least I’d put money on the M1 not being deprecated before all Intel-powered Macs (present and future) are deprecated.

In other instances where Apple does have access to your data, there is a plausible justification for that access and no evidence shown where Apple has ever abused that access for commercial gain.

I've heard this from a few people recently, but I don't understand the implied criticism. What should Apple do here? Keep my data mostly private but also slip a copy of it to Google and Microsoft?

Obviously not. Through the high purchase price of their products, I'm paying (and trusting) Apple to manage my privacy and keep it private from everyone else. The fact that "everyone" necessarily includes all of Apple's competitors isn't just irrelevant, it's a red herring.

I realise that capacity is theoretically orthogonal to swappability, but functionally it's relevant because battery casings, compartments, connectors and chassis strengthening elements all take up space that could otherwise go to a larger battery pack.

Your analogy misunderstands audio signals. The resolution components of bit depth and lossy compression are different axes and should not be conflated with or analogised to frequency resolution. They behave very differently.

But let's say your washing process is different to mine. I'd still rather do two trips upstairs than fold sheets.

Twenty years ago, such files would have been barely listenable. Ten years ago, this would have been tolerable but obviously compromised. Today, with the best encoders, 128k MP3s are shockingly good. Certainly not perfect. But good.

MP3 encoding has come a long way.

Of course, when you look at these high resolution recordings, the amplitude of material above 20kHz is piddling. The amount of harmonics/overtones in acoustic instruments is minuscule in the first place.

That usually means one of two things—

1. the frequency response of this new system is different, changing the relative loudness of different instruments;

2. the context caused you to concentrate on the music differently and your experience of it was therefore different.

The critical thing nobody ever says is "I heard things I never heard before, then I went back to my regular system and I stopped hearing the new thing." That never[0] happens—because the thing you hadn't noticed was there all along.

[0] Edit: Okay yes, so not never. I was assuming that the regular system is a reasonably competent modern setup. The median intentional audio system, shall we say.

(I do fold sheets for the guest bed but that’s because the alternative set might spend months on the shelf. Most of the time the same set is washed and put straight back on the bed.)