Welcome to CAP Alex!
Well, Referspot is not a member here, so we can’t ask them directly.
With the recent increase of CPA fraud however, I must assume that is the way they protect themselves. Some programs, such as Adriches, have recently totally removed the CPA option.
I personally don’t do CPA, I find it a money loser.
But I know some of the other members here do, so stay tuned for someone with a better answer.