I've tried Extreme Rules a couple times (Less than 10). What caught me off guard was money manipulation is allowed while all other advantageous things are not. Is there a reason for this? Was it discovered later? I think I may try to run it but I am not going to use money manip because that feels off to what it would seem to be.

oh, and this isn't directed at anyone. just saw some youtube videos with it in it as Extreme Rules. just trying to get clarity. Thanks again

My opinion:

Money manipulation is not a glitch, because you can get the same result by playing normally. The old route was just to keep saving and resetting until you got +50, then save and try again. That would fall under "regular gameplay".

Also to answer your other question: Yes it was discovered later. It's also why bomb upgrades are permitted, as it came before a time when counting to 10 to get bombs was not known! It's a very old ruleset from what I understand, which is why there are what some might call odd concessions allowed in it.