"Flash" - used for doing n balls for only n catches, but also used for throwing things higher out of a running pattern.
Generally, names that aren't at all descriptive of what they're showing. Even abstract similarities (slams, levels, etc) I prefer to something like "someone's something". Not so much of an annoyance for old stuff, but now that we realize how much is out there, I'd prefer for names to be more descriptive. If you want to credit the inventor/popularizer that's fine, just make the bolded something descirptive.
"True ____". Why are box and true box different things?
I don't have a problem with "qualifying". I see it as a useful line in the sand, rather than any kind of authoritative claim. I don't see it as even implying that 17 catches of 9b isn't juggling.
I typically hear "isolated" in the context of an "isolated endurance", which makes sense to me. I do not think it's ideal terminology. Perhaps "stationary" or something would work better, to avoid the rare (ever?) overlap of someone doing prop isolations while also meaningfully not moving their feet.
100 % agree with everything you say about best trick competitions.