I completely forgot about this <hmm, I wonder?> question. So I just went out to the shop and did this test.
test rig of 60 volt DC power supply, 7 to 70 volt PWM variable speed controller, ancient PowerFist single-speed universal AC/DC power drill.
Results? Works just fine, oscilloscope on motor leads shows nice clean signal, no smoke. I’ll do some torque tests when I have some time this weekend.