FWIW, I think the suggestions made here and elsewhere that PCs have to be at full health before any fight are rubbish. Often enough, in the games I've played, there are time constraints that prevent players from taking 10 minutes, let alone 40-60 minutes after every fight to rest & treat their wounds. Fortunately, the existence of clerics (and a few other classes) who have healing spells and powers and the existence of items like healing potions help make the action a wee bit more dynamic. And if the PCs are wounded and they think they're heading into a fight, maybe they'll pay a little more attention to the terrain and their tactics, rather than just charging the foe and trusting to the DM's aversion for TPKs to carry the day.
I could be wrong, but this reads as a comment on D&D and rpgs in general, not as a direct reply to the situation in Pathfinder 2, specifically on official adventures.
Frankly, I believe that if you just play one or three official Paizo adventures you will quickly be disabused of that notion. You don't
have to be at full health, but it helps
much more than in any comparable D&D game.
With just a little bad luck even the strongest Fighter can go from max to zero hp in a single round. If he started out at half, there is a considerable risk the monsters could down a second character as well. This can spell disaster, since even the best Cleric has limits on how much she can heal - especially if several party members need to be healed simultaneously.
My experiences are clear: going into even a "Low" encounter at half health can quickly turn into a nightmarish fight, where the party needs to expend all available resources just to come up on top.
In stark contrast, going into the same encounter fully topped up significantly decrease the risk of entering "emergency mode" where you need to stop coasting along (using your unlimited actions and cantrips) to go all-in, that is novaing (using up consumables, magic item abilities, and your best spells - including Heal) just to survive.
I have GMed a lot of D&D adventures, and I am absolutely used to being able to use time constraints to spice up the adventure so I fully get where you're coming from. But I have found that this pretty much
does not work in PF2.
There IS a way to express "you're beat up but heroically keep moving" but it doesn't involve adventuring at half hp. Instead it involves the usage of Conditions (such as Fatigued or Drained).