I had some GAC encounters where my opponent did this (remove mods after GAC lock).
But it is not always clear if they do this deliberately (to fool gac opponents) or because they have limited sets of good mods and thus need to shift them around to accomplish raids, tb and other events.
In any case, it does not matter much. The only thing I can think of where this might have minimal impact is with speed critical teams like DR/BsF. There was a time I might want to avoid using my DR team on defense, if my opponent DR/BsF is faster than mine. And if I cannot see that before the match start, it might be a problem. But again, this is not that relevant anymore since we have other teams beating DR consistently nowadays.