It is a bit like that.

If God existed and wanted to have people believe in Him, He could prove His existence to us. Write "Hey guys, I'm God and I exist" in the stars or something.

If scrypt.cc was mining and not simply paying investors with their own deposits and wanted to prove it, they could provide proof of solvency, and show us the blocks they are mining. Write "Hey guys, I'm Scrypy.cc and I'm mining" in all the coinbases they mine or something.

Neither chooses to do so. That doesn't prove that they aren't real, but it leaves room for doubts that could easily be avoided.