kill nodeos without -9 cause "replay required"

[bixf]

in #4301 it was said that when you stop nodeos ,use kill pid without -9.this is the safe way that doesn't cause replaying the chain. but this time after i killed the nodeos, it still need to be replayed when i restarted. why this happens? is there a clean way to stop it, or is there some specific timing doing it?