Well in Manchester derby you had Martial injured early in second half when he crashed into the post (was treated for over a minute), there was also a Man. City player down and minute VAR check on the Aguero offside. Add in all the subs and five minutes was right.
I can't remember the last time there was a close 1-0 game and there was only 2 or 3 minutes added on tbh. Four is always a minimum in those circumstances.
If you actually did a proper stop clock like in Rugby then the ball is rarely in play for more than an hour so would be even more injury time than Fergie demanded back in the day.