Agree. Have seen it at United as well on occasion.

Also just experienced it at the Fast Track security position where they x-ray your carryon before you enter the airside terminals at LHR.

Only about 20 people in line in this priority Fast Track lane, but it took about 45 minutes as they kept bringing people who were "late" for their flights to the front of the line.

I managed to get to the airport 2 1/2 hours early. Why couldn't they?