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Justin Mathews wrote:

I don't fully understand why PWM in audio is considered analog,
though. I understand that DSD (for example) uses sigma-delta
modulation (a kind of PWM) at an extremely high rate -- the averages
between duty cycles create a reconstruction which is
indistinguishable from the input.

That's the idea. 1-bit sigma-delta aka DSD is as far from analog as it
is possible to get.

(as seen here?
https://www.analogictips.com/pulse-w...odulation-pwm/)

That's PWM, not DSD. PWM can be digitally or analog modulated. PWM has
been used in electronic control circuits for at least 50 years: no
digital control required.

Based on what I'm reading about PWM, it still seems inappropriate to
call it "analog." I'm not sure what I'm missing...

From the dictionary definition,

adjective: analog

relating to or using signals or information represented by a
continuously variable physical quantity such as spatial position,
voltage, etc.

The width of the pulse can be continuously variable in proportion to
the voltage, and in that case it is alalog.

Andrew.