3 mins in extra time is more than usual, it’s usually just one. 6 mins were added in after a 45 min half compared to 3 mins at the end of a 15 min period. It should have been more but never likely to be much more.
I think it’s unfair to blame the players for not getting anything back. It’s much easier to come back at the end of 90 mins than after 115 - 120;mins. Both sets of players were dead on their feet. Neither team were fluent which suited the team with the lead
Stoppage time is determined by the amount of stoppages in the period leading up to it. Simple as that. There was a hell of a lot more than 3 minutes worth of stoppages in that 15 minute period of second half extra time!