Oh, you can do that, but it would be a foolish thing to do. It's great for knowing how long you can sit there in the backyard with four or five servos moving. Your idea of "average draw" is great, too, if a person actually knows what that is.

The point that you simply don't seem to be understanding is that you are recommending that people measure their system's capacity with an artificially low current draw, and use the time measured in order to determine the amount of time that is safe. I think it's great that you've now couched that highly specific method with "back[ing] off from what is measured for safety's sake" which surely wasn't in your initial bit of advice to Delbert. You want to use a fuel tank analogy? Use the right one--what you've suggested is the equivalent of seeing how long the engine will idle on the ground until out of fuel, and believing that to be an accurate representation of how long an actual flight could last.

Yes, I'm judging your advice. If you don't like people doing that, I'd suggest that you refrain from offering advice. We all form opinions about what we read. When we answer a question, we've got a responsibility to answer it based on either first hand experience or real knowledge. You've suggested methods that will lead people down the wrong path. You're unwilling to retract that advice, for whatever reason.

Does increasing the amount of airflow over a deflected control surface exert more pressure on that control surface?
Does more pressure on a control surface mean that a servo has to exert more physical force to attain or maintain a given position?
Do servos "fight" engine vibration, exerting more force to maintain a neutral control surface position than when an engine is not running?
Do servos draw more current when they have to exert more physical force to attain or maintain a given position?

Most of us can figure out that the answer to each of those questions is yes. Do you disagree? That article from Central Hobbies that I mentioned gives a measured current draw of 95mA on their test model (which is likely to be a YS four-stroke pattern ship, given what they sell) without the engine running. With the engine running at full throttle on the ground, the current draw went to 375mA. That's a huge difference, and the model isn't even flying. Is that a model that's likely to be representative of what is usually discussed here in the Beginner's forum? No, but the basic concept is still valid. It's very unlikely that a .40-size trainer will see a current draw that high from just running up the engine, but it surely will see a markedly increased current draw.

You gave this neat, simple little collection of methods, at least three of which bear little relation to what actually goes on when a model is flying. You can keep trying to put lipstick on that particular pig if you like, but it's a very bad idea to suggest that other people use those methods. If you want to do that yourself and try it with your models, that's your choice. I rather doubt that you have.