No its not true
Often councils have their own policies which are not always consistent with the law
She needs to look at SEN Code of Practice & Education Act 1996 & SEN toolkit which sets out when a statement is required. Its usually when appropriate progress has not been made despite school taking all relevant measures / external advice or where the provision required cannot be met from the resources of the school. Adequate progress is defined in lots of ways and can be inadequate given the IQ of the child.
It is also not just about academic scores - children can be behind on language, social skills, behaviour but still scoring well in academic tests.
DS is in year 1 and he has been statemented since he was 3. (It took two appeals)
He had average intelligence but moderate autism.
He has never been 4 years behind academically. I suspect most children with autism are not 4 years behind by age 5-6. They might be later on once the work moves from rote learning to more complex skills.
My DS is ahead with reading. His spelling is ahead. Socially he is 4-5 years behind. Language he is 2-3 years behind. His behaviour (due to good intervention) is really good in school. He has fulltime support in school.
Look at IPSEA website for info & links to doc on how she can apply for a statement herself. Many local authorities have policies which lead to applications being rejected on silly grounds - really its just delay and gatekeeping of money.
If she has any money herself she might want to buy private support eg private speech therapy or ABA - prove her son can do better - and use that evidence to ask for better provision. Its not always necessary to do this but thats what worked for us. Otherwise it is argued its the autism thats the problem not the school / teaching so if you can prove your child can achieve much more with better quality provision then they cannot use that argument.
I can guarantee even if she does not get a statement she will end up with more provision by applying and appealing any refusal than by sitting and waiting. Even if she does not end up with everything she wants, it will be more than getting now.
Schools do get a bit of a hard deal - the government and councils say they are skilled up to cope with autism and force them to take children when most schools really do not have a clue what they are doing. They are also fed terrible advice about how a few symbols and a visual timetable is all that is needed when in reality the child might need a completely different teaching method. Most teachers have never seen good autism intervention so actually do not know whats possible. Your friend should also explore any asd units or schools (state or private) in the area or surrounding areas and go and see what they offer.