In China it turns out there are lots of rule sets. The city I'm currently living in (Changsha) has it's own ruleset for example, with less tiles than these examples.
mahjong rulesets are wild. I play Japanese mahjong, and the difference between online and a mahjong parlor is quite different, making it interesting to see what people optimize for in those different settings
I think mahjong is probably "house rules the game" though. Pretty sure most mahjong hands probably just were a result of some guy being like "hey this hand looks like it should be scored man".
It's similar to dominos then - every region and cultural/ethnic group has their own variant, and every family has their own house rules. Or craps! I was so confused my first time playing in a casino after learning to play in the streets.
In China it turns out there are lots of rule sets. The city I'm currently living in (Changsha) has it's own ruleset for example, with less tiles than these examples.