Identifying when to throw those last few hit points in the trash and call the fight a “win” for the adventurers is part of what separates a great GM from a good GM.
Your games pacing, the spotlight moment for your heavy hitters, and respecting your players time and emotional investment in a combat scene, are all much more important than the big bads last 10 HP.
I definitely had some specific games and circumstances in mind. The core of the message is “feel free to do what is right for your game, don’t be bound by the rules.”