You're right, this actually does vary by jurisdiction. I looked into and was quite surprised that the UK allows something called "compensated game control" to adjust the odds dynamically so the observed payout matches the expected one. [0]
Nevada has the opposite rule: machines must only incorporate chance when paying out and the theoretical payout is what the gaming commission analyzes. They can't dynamically adjust odds to favor a preferred payout. [1]
Nevada has the opposite rule: machines must only incorporate chance when paying out and the theoretical payout is what the gaming commission analyzes. They can't dynamically adjust odds to favor a preferred payout. [1]
[0] https://www.gamblingcommission.gov.uk/authorities/guide/page...
[1] https://gaming.nv.gov/modules/showdocument.aspx?documentid=4...