Ok, I agree I have no idea what you would do to weld some super alloy, mostly from the perspective that the same rods that are used with TIG are not used with gas welding (though based on long observation of TIG threads, the "right" rods aren't always used there either).

I'm not so sure I really agree with the thickness thing, you can straight forwardly weld .6mm tubes with gas, that is business as usual with ultralight aircraft. Is there a lot of thinner welding than that gets done on bikes? Cause that isn't pushing it with gas, that is without moving down into jewelery range torch heads. For big guys like me the light tubing is out of reach anyway.

As far as skill is concerned it is the same skill for the most part, except no pedal. Some courses teach TIG by introducing gas welding first. I am not sure why they do that, except that if they are teaching all the skills, gas, MIG, stick, TIG, I suppose it makes sense to start with gas.

I do think that if one wants to start turning out welded frames for the punters it makes more sense to splash out for a Dynasty 200, than to fritz around with gas. For the Hobbyist, not so sure. Marginal cost of 75-100 bucks is pretty attractive for welding with gas. I spent more than that on the diamond wheel that sharpens my tungsten, and new it was hundreds.