Since none of the two networks have any kind of action tracking for advertisers, creating a ref for each network seems like a logical thing to do.
It is most likely the HYIP platform itself that use such a ref, when they first launch.
Both Coinzilla and Mellowads seems to have a rather high ethical standard, so personally I find your theory to be ridiculous to be honest.
Theoretically you don't know if a program is a scam, before they actually scam. For the networks to turn down such advertisers would be bad business.
Even Google run these kinds of ads.
if you see see 7% daily forever its 100% scam ponzi. And if take good attention you will see only the ref links to same kind of ponzi's. and if you dig deeper you will find same css styles in coinilla.io and mellowads. i think nobody realy takes attention to it and just follow the mainstream of new hyips. if i was mellowads and i see a scammers uses my service as reflink i would ban him. but yeah people only want money those days.. waiting for reply from ad networks lets hope they dont ban me from using them as service its just a question im stuck with long time..