I didn't test sleep/wake consciously while I docked my laptops, but I don't remember they start making sounds when they should be silent. Maybe you're seeing PowerNap cycles, but mine is not doing any noise in PowerNap, either.
Need to test with leaving Firefox playing something and see what it does.
...all in all, interesting sentiments. I'm using these things for ~15 years at this point, and while they did funny things in the past, this was not one of them.