I think you have to be careful about making assumptions based on “not” seeing something. The old saying, absence of evidence is not evidence of absence, etc. Rusty doesn’t actually have this phrase in his working vocabulary. I made him do it in the interview, and he was able to, despite not actually working on it. That was more a demonstration of his ability to figure out stuff intuitively, which is super high. I think Rusty is generally underappreciated for how many techniques he is able to do.
What you really need to look at are players that can actually play this line with pure alternate, and do so in a memorized way without thinking about it. And really, Batio is one of the few I can think of. He does it all over Speed Kills, and In our interview he did it just as effortlessly, starting on both upstroke and downstroke, without breaking a sweat. It’s clear that it’s memorized for him.
The upstroke version uses swiping, which we haven’t talked about it, but is physically very easy to do once you learn how. If you have a reliable alternate picking motion that you can do smoothly without fatigue, then you can have this version on your worst day with minimal warmup, seriously:
If you’re looking at players who can only do fours on a couple strings, or only on their best day, and they tend not to play it most of the time, my guess is they never really learned it. You can’t really make the assumption that it’s because the technique is too hard. With some phrases, it’s just less obvious how to do them correctly, and that’s why you see fewer people doing them, not because they’re physically more effortful to do.
Again, I like all solutions. Economy is great and alternate is great. Not arguing for one or another, they all get a fair shake!