They don't have to fallow it because they aren't selling steam keys on itch.io. They are giving the game away and leaving a link in the description to there steam page so you can buy it on steam. Witch is a good way to do it. I wanted to sell the steam keys on itch.io though because if I sell the keys on here steam doesn't take 30% of the sale i only have to pay itch.io 10%. Also on itch.io if i wanted to i have access to a slider that alows me to decide how much of a cut itch.io takes i can let them take 50% or i can give them nothing. So sence im selling the steam keys on itch.io I have to fallow steams rules or I won't be able to sell my game on steam. And there number 1 rule is that you can't sell steam keys for cheaper then they are available on steam. I left the full game as a demo so if you don't want to pay you can still play without having to pirate the game and possibly get malware. I understand it's strange so I'm trying to be as transparent as possible as to why I'm doing it this way.