Adjusted XP or not?

[MaxWilson]

The "challenge" label only really has meaning in the context of a full adventuring day.

Not according to the devs. Crawford says they balance encounters assuming that PCs are always at full HP.

We actually balance the game assuming player characters are at full health. We have to do that, since an encounter could happen at any point. An extra powerful healing spell doesn't unbalance the game. But it can disrupt what feels right to a group. That's what concerns us.

Ref: https://twitter.com/jeremyecrawford/...964290?lang=en

Anyway, the point is, the game really does overstate encounter difficulty. Deadly = "not necessarily a curbstomp". IME Deadly x3-4 is approximately the tipping point where good tactics are required to guarantee a win. Fights at Deadly x6-8 are definitely in the monsters' favor, though stilll winnable with good tactics. Medium/Hard/Deadly x1 are still basically guaranteed wins for the PCs unless the DM is deliberately exploiting the holes in the CR system, e.g. by using relatively overpowered monsters like Intellect Devourers and Banshees, or overpowered combos like Yetis and Hobgoblins.