Nat 20 is very, very commonly used by GMs to mean “critcal success” in or out of combat, no matter the explict rule. Same goes for nat 1 being a “critical failure.”
Why? Because it makes the game better for everyone to have these rare rolls rewarded or hilariously punished.
Bad faith and pedantry aren’t the same.
The comic very clearly implies that the nat 20 caused their dumbass character to be able to decipher the runes.
If it didn’t, the player wouldn’t have announced “Nat 20”, but the actual score, wirth modifiers taken into account.
Nat 20 is very, very commonly used by GMs to mean “critcal success” in or out of combat, no matter the explict rule. Same goes for nat 1 being a “critical failure.”
Why? Because it makes the game better for everyone to have these rare rolls rewarded or hilariously punished.
The trouble with doing that is that you end up in the stupid situation described by this comic!