Just a hunch...

But I get the feeling that McVay's first read for tossing a red flag, (unless the play is directly in front of him), is reaction from his player.... which could be the case for many coaches... but it does confuse me. They have instant ability to see the replay, unless they're in a neck brace, so taking the word of the player seems not a good decision maker. Receivers WILL insist they caught ball, for example. - JamesJM