i think you mean its not a conventional affiliate code, it is still a referral code, there is no hard requirement for a referral code to make money for the referrer, but yes this is indeed a mechanism that steam has and steam tracks these referral IDs

theres an explanation on steamgifts about the referral codes from 6 years ago, explaining the mechanism, and how it tracks the click as a +1 without any sort of purchase a requirement past that, with enough +1's the curator gains more weight over other curators for recommending games, which could be leveraged indirectly by a curator to accept sponsorships to advertise or promote

https://www.steamgifts.com/discussion/3Y4jr/curatorclanid

the link includes a nice way to catch these too with ublock filter

steampowered.com/*?curator_clanid=$document,important