We've been through this before, so worth it to search a bit.

Briefly: on long climbs, some people can stand for much longer than others, and those folks are obviously working in an aerobic range. They also practice in that position alot. <------ This is 'a clue'.

If you tire after 10 seconds or so, you've obviously gone anaerobic. Fine for climbs of, say, 9.5 seconds or so.

I think to consciously make the effort to forcefully pull your legs up during standing is odd, and probably exhausting.

Oh, and I have to shift at least three gears up when going from sitting to standing. One or two isn't nearly enough.