I guess these worries are depending on how sensitive you think your batteries are. With gels I would worry, flooded cells not so much.
Going from bulk to absorption is only voltage dependent, all parallel controllers will see the same battery
voltage and will reduce current
to avoid exceeding the setpoint. I have not seen any hunting/fighting between the controllers.
Going to float is a funtion of time, if you really have 3h in absorbtion with your 840Ah bank, they all 'should' go into float. One controller may keep the absorbtion phase longer than the others but will also finally switch to float voltage.
You could set 3 out of 4 controllers to a lower voltage setting and only have one set to the max for your battery
type. But I call this overthinking it.