So, what you are saying is that they DID not come from the Prophet but are falsely attributed to him some 300 years later. So, basically, they are 'hearsay'. In fact, all hadiths were written some 200 years after Muhammad died. Thus, they are all 'hearsay', yet are used as another source besides Quran.
Plz don't jump over the bandwagon, i am not implying that Hadith are heresay, just that they should be analysed logically.