I tried again today with a new activity profile and autolap disabled and it worked as desired!
I can reproduce the issue now. If I have a profile with autolap enabled and select it, then go through the menu and toggle autolap off, and then start the workout, manual laps won’t show in lap data fields. But if I load a profile that has autolaps already off by default, manual laps are reflected in lap data fields correctly. So if I change the autolap setting, I need to exit to the watchface and reload the profile to get it working all the way.