[...]
With a digital volume only the signal (music) gets attenuated as you turn the volume down, the noise level remains the same. So as the volume goes down the dynamic range / snr goes down.[...]
That's the only bad thing I was thinking myself too, I'm glad you found the perfect words to put it out nicely.
Based on the already published measurements, I see no concern that someone will be actually hearing any noise out of HPA1. Instead, putting a...let's say 2x47KOhm pot in front of HPA1 will add lot of noise when volume's to the max.
P.S.: However, sometimes we need to work backwards from what our customers want, no matter the measurements, so perhaps a volume knob might be added later anyway, who knows?