Apple stretched out the review process before rejecting the app, and after I escalated to tcook's email address, I received a call from their team telling me my app took "measurements the Apple Watch was not designed to support".
This, of course, is complete BS since the whole point of generalizable sensors and Apple's ML tools is to build apps to add new capabilities to the device, otherwise all we'd have are map and messaging apps. And it's slightly comical that they added the feature to detect hand washing in the newest WatchOS, something the Apple Watch "was not originally designed to support". I'm fairly certain they didn't want to have any part or apparent liability for the app if it "didn't work correctly", nevermind the app did not mention COVID, disease, or anything else controversial.
There was always a way to "escalate" or "appeal" a review, so any new processes are smoke and mirrors. Apple will always reject whatever they want to reject until they're forced otherwise by a regulatory body.