I just assumed he had an early chance to test it as he is a games tester for SCEE
He wouldnt have been offered that privilage seeing as SCEE (as a company) would just test it in house with their own employees and wouldnt release it outside of said offices and it certainly wouldn't put ANY of their staff before a consumer. Believe me.
Plus SCEE dont have a working copy of it as of yet. Only SCEA. He's either a qualified hacker and has somehow aquired it or one lucky individual, but no way would Sony just LET him test it cos he works for them. IF he does at all.
Tbh i'd rather have the finished thing cos as with most demos it will probably change in content and what he tested wont be the same as the finished product.