I believe this guy is telling the truth as there is really no reason for him to make this up. The only reason it works is cause the PS3 he copied it to didn't have a PSN user signed up therefore it didnt/couldnt say the save belonged to another PSN user. So you can prolly make the trophies pop, sign up for a PSN user after they pop and then sync them. Not really that useful but still...
EDIT: Tried with my save on a new user with no PSN signed up and it doesnt work.