I assume (maybe incorrectly) since the title of the thread is "controlled group" that it is really an affiliated service group partnership of professional corporations. So each doc has a separate 100% owned PC. So the doc is an HCE due to ownership of the PC stock. Assuming the PC is a partner in the group it's an ASG. OTOH, if the doc has a separate PC and neither the doc nor the PC has ownership in the group, it wouldn't be an ASG or CG.
If all the docs are directly employed by the group then you are right the doc is not HCE unless also a 5% owner.
To channel Larry Starr, we can't really answer properly without complete facts.