Ponzi or Scam exchange service?
Probably both.
Common exchange script used on many sites, nothing custom or worked on
The % is new though probably some BS by the owner.
You even mentioned
"...not a regular ( ponzi ) investment" blah blah at the start. Basically admission to ponzi
Exchange service. And are you kidding? Nothing custom worked on? It is fully custom made script. It is nothing default.