With this config enabled, if a player kills another player the killing player does not need to wait to be able to loot the grave.

Any other player would still need to wait as normal.

I believe there's already a feature like this in place. Either it's what you're asking for, or it's only allowing the killer to grab the grave. Can't remember how I've done it. Right now I don't have time to test and such, so let me know if you want me to change anything. Also let me know if this comment solved your issue, so I know if I should close the issue or not

I was wrong. The config just allowed ONLY killers to loot graves. I've now changed it so that killers can loot instantly (as well as renaming that config to killerSkipWaitTime.
This change is implemented in latest releases for 1.20-1.21