I see now that you're referring to accumulation of yellows. Reds still count for the premier league so a retrospective red would mean he is out of for 3 games in the PL.
Have you got any links as that's the first I've heard and doesn't appear to be any reference to it in this document?
http://www.thefa.com/-/media/files/thefaportal/governance-docs/player-essentials/2018-19/essential-information-for-players-2018-19---steps-2-4.ashx