Nice post Ben.
Look, if you get all 10 reps for 3 sets, you up the weight by 2.5kg.
If on the next workout you get 10,9,8, you attempt the same weight again.
If by some miracle you do 10,9,8 again, then you need to add a set. If you did 10,9,9, you did one of the 3 MORES, you progressed, on you go.
As long as the session is progressive, you'll progress. If you repeat a session, then you've gone backwards.
If the weights are getting heavy and you have a back off week, this rule doesnt apply. No one on this forum needs a back off week. Yet.