First, I want to know that McVay is even helping Goff with audibles. We don't know that for sure. If so, it's fine by me, whatever works. If not, then it's a non-issue. All we have is hearing someone's voice in the headphones late in the setup for the play.
But all teams will show cover 1 and play cover 2, or other combinations. They disguise the coverages. So, the coaches seeing the disguised coverage is no help in calling an audible. Usually audibles are from pass to run or vice versa. Or if it is a run play, with a pass option (RPO) like the TD to Watkins they maybe be able to change a route from a slant to fade or vice versa...
But in terms of disguise I'd guess is happens on 90% of the plays, maybe a little less
