It's not about the queens, it's about the drones (male bees).

The workers only start laying eggs if the hive goes without a queen for several weeks, and either way the eggs they lay are unfertilized and therefore cannot be raised into new queens. So requeening it is certain to work in that regard.

However, unless you euthanize whole hive, the aggressive drones will continue to live for a while and can mate with queens in neighbouring hives and spread the aggressive genes that way. So there is an advantage to euthanizing the whole hive instead of requeening it.