Early intervention????

Hi im fairly new to all tjis snd feel a little in limbo. my son is 3.5yrs and he has been having speech and lang therapy and me and my husband asked for a referral after we noticed lots of traits of autism. The therapist said she'd picked up in things too so she made the referral. We havnt even had an appointment come through yet for paediatrician and his pre school have said they want to do early intervention. Will this interfere with an actual diagnosis if people are saying different things that are observing him to what the doctors see that are actually assessing him. They have also moved him back a few stages on his development charts so they are more likely to get funding to have the early intervention. Im really confused. Any advice. Xxx