The only animal I would consider "at rest" would be a bedded animal.
If they're on their feet, they're entirely capable of moving. So again, don't delude yourself into thinking otherwise. You have no control over that animal's movements. Your call is a guess, not a given.
Don't think you are, but if you're shooting bedded critters, then that's a whole nutha mess to address. At least they'd be "at rest" though...
As for hunting only when there's no wind, I'll just LOL! I live in the east & have hunted all over the country, including out west in the mountains & on the plains. In the mountains, there are these pesky things called "thermals" that can & will affect bullet flight, same as "wind". And there's never, not thermals. Similarly, I haven't been out on a prairie yet, where there was "no wind". Even back east here, there is NEVER a day that I'm not holding wind when shooting 600-1000+ yards. Literally, never...
Don't know what 'vacuum scenario' are you guys shooting in, but I know enough to know its a rarity, when it happens.
Same rules apply to archery, BTW. Time of flight is relevant to arrows, too.
And yes, I'm also a bowhunter & subject myself to the same critical observations.
Not judging, just keepin' it real. If you guys' reality involves regularly encountering an atmospheric 'vacuum scenario' with frozen stiff animals to shoot at, then consider me jealous! The animals I hunt are mobile, and the weather I shoot in is anything but a non-issue...
Take care