*If not however Helldritch is doing it, by the 'resting means ending the play session' or 'the opponents/treasure will flee/regroup if you go out to rest' method with which you and I both started, I suspect.
Easy, we voted upon what we wanted as groups. 12 players and 1 DM (me). We analyzed how the game was supposed to work and we checked if optional rules, if any, would help us reinforce the play style that the game was advocating. Without ensuring the number of rounds, expected combat per day and a wish for a minimal lethality in the game, you risk to see problems with some classes.
1) Short rest classes will be disadvanted over long rest ones. As shorter encounters in shorter rounds will tend to favor the Nova style, the 5mwd and will make pure martials like trivial.
2) Martials in particular will be left in the dust. So will monks and casters relying on short rests for boosts in damage.
3) This will break a bit of the narrative as after a fight, long rest classes will want to rest...
4) On the other hand, too many fights can also break the narrative, as long rest class will lag behind.
5) It is all a matter of pacing. For all its qualities, 5ed failed to explain the whys and hows of its design. A new DM must read a lot or be coached into how to drive the game. It is a case of easy to learn, hard to master.
The balance is there, it is just that some misses were obvious (beast ranger, monk of the elements...) and the fixes were easy enough to do but were not done at launch. And as much as I hate TCoE for a few things, it did corrected a few bugs. Not the same way I did, but at least it tried. (Just adding Ki for high wisdom made monks quite good in our games.)
One of the failure of 5ed is that it tries to be both a narrative game and roll game at the same time. My feeling is that the narrative side of RPG is a bit more proeminent now than it was a decade ago. Example is the CR YouTube show. The narrative is much more proeminent than in many games/table of D&D I see. It is now a model by which many tries to stick to, but the rules as they are do not really and fully support the style. Especially with inexperienced DM or players that are there for the win and not the story. Matt's players are actors that understands the value of sacrifices for the story. Most players are not in that category.