The rules state that all reaction counters are pulled from units at the end of the turn.
The rules state that the regroup command that only happens in the command phase removes all suppression and reaction counters.
How could there ever be reaction counters on units in the command phase of the side that is about to execute that phase? They are all removed at the end of the last turn...and no reaction actions are allowed during the command phase so no reaction counters could be placed on units of the player who hasn't taken his command phase yet.
Hence there is no way there could ever be reaction counters on units eligible to regroup in the command phase.
Someone else might have posted this... but it happend to us this weekend... During command phase, my oponenent destroyed my walker... I had the damage that caused a reaction token to be placed on units in proximity...
I would guess they said removes all reaction and suppression counters to future proof against new rules or units that might make this possible, and/or to stress that the action totally clears status markers on the target unit.
The act of giving them an order in the command phase gives them a reaction marker, that the order of regroup immediately lifts- it means that when you are given a regroup order you still get two actions and can react in the action phase, but if you are given a command phase action order, you get a reaction marker and annot react/can only take one action in the action phase.