I’m guessing they only did it like that for the benefit of other players, so engineers can tell who’s already been buffed, and enemy players can prioritize targets.
I can see that being pretty helpful for the engies, because you could waste a lot of time guessing, but I don’t see it as necessary for the opposing team’s players.
It’s too bad they couldn’t come up with an alternative method to alert the engineers, otherwise it could have been contained totally within your own HUD.
