So I'm convinced at this point that the Sents have different aggro levels depending on what planet you are on, in addition to their numbers. Some don't give a shit that you mine, some give a little shit (by doing that scanning thing, which is I assume a warning), and some give a hefty shit.
It's a true pain in the ass to find that out by trial and error. Luckily you can dodge them by sitting in your ship or going in a structure (which makes no sense to me, but whatever), but it's annoying if you aren't near those areas.
And apparently, if you do happen to get one of those more aggressive Sents, have fun getting jumped for picking flowers. I took a valuable bulb from plant, and I instantly got shot up to three stars. Whether it was a glitch or because of the plant itself, I dunno, but if it's the latter, that's stupid - you'd have no idea until you collected it.
I feel like certain things in NMS are great but just aren't executed well when put into practice.