You tell us, those questions are not relevant to the problem or original scenario.
Which is it and why does it matter when the original scenario happens at the table
Players: we hunker down and take a long rest
Gm: you can only do that once every 24 hours and it hasn't been long enough to take another
Players:

okayyyyy... so we setup camp and finish our long rest tomorrow after 24 hours pass
This is not the issue. Of course you can try to wait for that. I say try, because wandering monsters are often a thing and chance can disrupt it.
The issue is whether there's a time pressure or not, and there almost always is.
You crossed the wires on who is saying what. Nobody. Particularly cares why the recovery can happen after resting 8 hours once every 24 hours. The issue is "

okayyyyy... so we setup camp and finish our long rest tomorrow after 24 hours pass

"
Some people have been arguing that PCs know the mechanics because they can see what happens in the game world.
Channeling that same batch of players again that bold but can be answered as follows: "well I know the gm won't sacrifice the campaign over this and don't think this will make them walk away mid season so it doesn't really matter but you can be 1000% certain more of the group will roll up short rest PCs next game or next swordbush ASAP if I don't like it"
I won't sacrifice or save the campaign over it. If the group rests and lets the cultists prepare to the point where they can't win, that's their fault, not mine. It's my job to have the world react to what the PCs do or don't do as the case may be. It may very well be that the cultists are unable to prepare much in the way of defense. Or they may. I'd have to know the specifics of the cultists and that location to make an actual call.
And rolling up only short rest PCs has other consequences. Long rest abilities are generally more powerful, which is why they aren't short rest abilities.
It really makes no matter to me. The world is going to react to what the players do or don't do, regardless of party make-up. I couldn't care less which classes they pick.
If the results are bad for the world then those players will look at it as an unwinnable scenario where they were punished because the gm runs a
crapsack world where the PCs never had a chance. If it happens repeatedly even after players switch to short rest nova build PCs it will eventually kill the campaign with players blaming the gm.
If the players look at consequences of their actions as punishments, they are too self-entitled for me to want to continue to play with. I'm not going to freeze the world so that a group of self-entitled players can have consequence free long rests whenever they want them.
DM: "You finish the fight and are exhausted. Most of your resources are gone, but you still have some fight in you. You hear from beyond the next door the BBEG's voice..."
Players interrupting: "We take a long rest right here."
(24 hours later)
DM: ...say, "I know you are out there, come through the door and let's be done with this!"
Sorry, I'm not going to just freeze things so that the players can always be at 100%.