It also can be quite difficult to make accurate judgement based on one evening gameplay, gettin 20-40X winnings all the time is not really only like 2% higher RTP but good luck as well
You can end up with really bad session as well with 94% or 98% TRTP, it's not change that much in hit frequency, size of winnings etc...
Happy that you had great session
It's tested quite a lot when these different RTP:s started to come real subject for providers and in reality it's extremely tough to see that 2% difference in your gameplay, if you are given same starting balance to same game in 4 different places and one have 2% different RTP, there really haven't been people who could say for sure that this game is running other version than others.
When making these changes to RTP:s, of course game providers want to keep gameplay near as possible what it used to be and if you take 2% off, little from there and little from there, these differences are really not easy to spot for people who play slots a lot or knows them very well after working in industry and testing them a lot.
I recommend to give it a try, let some of your friend to pick you some casinos where you have no idea which RTP is and then try to figure it out by playing without checking help file, i believe is harder what many could think. If you know it beforehand, then you kind of expect different behavior and are tempt to easier to "see" that difference but really recommend to take blind test, can be done with play money as well as they run same version of game than real money.