I did see a known Reefer with a Youtube channel who's said he had the issue you're describing with it reading twice as high as it should on more than one unit. I guess that's the person you're referring to?
I own a Seneye and I've not compared it to anything else but I find it has kept me from frying my corals. I used it recently to transfer coral frags from one tank to another and match the PAR in existing tank under Ecotech XR15's to Kessil AP9X's in the new tank. Being that all I'm doing is matching the PAR reading it's kinda irrelevant if the readings don't match an Apogee. In the Op's case I can understand the concern being that her she has no reference point.