I have just rewatched an old test and tear down of a "new" SBD Craftsman (argh!) drill. In it Da Bear wondered about a different method of testing "strength" vs his old pumping of water method. Well no load RPM can easily be measured and I'd bet it's no different from published specs. Where the manufacturer could cheat is torque, which is sort of what the water pumping test ... umm ... tested.
Why not measure torque like an auto wheel dyno does ? Measure the ability of the source to speed up a "drum" with a known moment of inertia. Then the torque is simply the angular acceleration/moment-of-inertia. The drum could be a grinder wheel, the type that's made to be driven by a drill, perhaps augmented to slow the acceleration down. While your cheapie Chinese RPM meter doesn't report out RPMs fast enough to get a true acceleration curve, you might be able to time from start to a certain RPM "good enough" to get an average acceleration. If that isn't good enough, a simple electronic circuit to time each revolution and log, reporting acceleration (instant and averaged) can be made (Arduino time !).
I don't know if Da Bear, or anyone else, is interested in this but it sure beats the expensive measuring equipment I've seen used on other YT channels.