This is one area where looking to the preceding games for guidence is tough. Since the resting mechanic in BG1/2 was always designed to be exploited and the whole game was built on the idea of saving constantly, because you'd be reloading constantly.
There were a lot of time sinks that made minor things take moderatley longer than they needed to, if the player was willing to just reload until they got the desired result. But it was never very strict. Resting without being ambushed, writing magic from a scroll, hitpoints on level up etc. Even rolling ability points for the character intitally. Most things were eventually handled via a game setting, like rest until fully healed or whatever.
Then you also had other stuff like the spell Haste, which was supposed to take a year off your life according to the handbooks, but which in BG became just a convenient way to boost movement speed and gain way more attacks per round than anyone should sensibly deserve, whenever you wanted, with no real downside.
Main point being, that if they want to make such exploits harder for a more hardcore game sensibility, it should be handled in the settings and built up from the launch menu. The default setting/mode should assume that the single player will save and reload frequently unless it is wildly inconvenient to do so. They can artificially slow the pace of the gameplay by making resting more difficult, but then the game needs to be designed in such a way that most encounters don't require a fully rested/buffed out party to manage. BG1/2 weren't like that at all. Pretty much anywhere and anytime you could save, you could find a way to rest, and the game assumed that the player would cheese and meta exploit encounters by resting or reloading constantly. It worked on a certain level because you couldn't save in combat. So you'd end up with choices like "oh shit someone just died, do I want reload to refight the battle? or just deal with the inconvenience of carrying the body to a temple?" But not too much beyond that. Pretty much every boss fight you'd figure on having to run it a few times, otherwise it wasn't much of a fight.
It seems BG3 is even more flexible and forgiving with its approach to saving, since you can save at any point, even in the middle of combat and death is just a knock down here, since nobody gets chunked. The combats themselves aren't nearly as fast paced or quick draw, and the load times are way slower. So reloading a boss fight in this one I think comes off as more of a chore.
I think they could explore ways to make resting a more engaging part of the gameplay, but I dont know if they should look to BG2 or the infinity games for that, since those games were built around easy rest at the ground floor.
