Hi, Aristoclis
I guess you engage them simultaneously during the cockpit prep because someone told you to do so.
I wonder if they gave you any reason for that.
If there is one, I will do the tai chi myself from then on.
I don't think there is a problem in doing it on ground from the point of view of the flip-flop thing, but who knows. Maybe its the reason for a later autothrust fault after take off or something.
In the air, there could be some scenario in which that flip-flop could occur and have bad consecuences.