It is good to de-escalate and keep discussions alive, which is the heart of the idea. But timing is key and the human condition needs to be factored in; We do get hungry, we do get tired, and these things affect our processing and how we approach problems.
There’s a dangerous implication in the “never go to bed angry” idea — You’re controlling whether your partner gets to sleep. I suppose some relationships don’t mind that aspect if it is mutual — But if you are truly tired, that is miserable, and it will affect how you approach that problem in the moment.
Anecdotally: I’ve seen this advice stem from a fear where the problem won’t be discussed the next day. Rather, actively avoided. That’s a different problem that isn’t about short-term de-escalation, but instead commitment and long-term resolution.