My ds1 needed to be taught how to roll over, crawl and walk and he still hasn't got a diagnosis of dyspraxia. His paediatrician always said drs. don't really like to have to diagnose conditions like dyspraxia until a child is closer to 6, simply because so many of the disorders overlap each other and the most relevant one in a particular case may not become obvious until a child is older, as some issues diminish whereas others become more acute with time. Motor skills in particular are an area where at age 4 there is still a huge range of what is considered to be an acceptable level of motor skill, whereas in a couple of years, the slow developers and the children with lifelong problems will have separated themselves out. There is also the possibility of physical causes that have to be ruled out, and it just isn't easy to get it right at a very young age - so lots of children diagnosed young end up with multiple diagnoses, because the initial one ends up not being quite appropriate, so another is added and so on and so on, until a child has a long list of disorders to their name, some of which are no longer appropriate, but which remain on their record because otherwise someone would have to admit to having been wrong in the first place.
Of course, this delay in diagnosing would be all very well if our medical and school systems actually treated a child's obvious symptoms without the need for a definitive diagnosis, but without a diagnosis, you get b*gger all help (which is probably only marginally less than you get with a diagnosis a lot of the time), and nothing in the way of closure - just the knowledge that something isn't developing quite right with your child and that it is not going to right itself on its own over time. And it is known to be important that a child with dyspraxia or an asd does better if they start getting help as early as possible.
If they suggest your child has an asd, but you feel strongly that actually his main issues are around motor skills, then argue your case - they can't accurately diagnose without a bit of help from parental evidence in any event. But most importantly of all, keep pushing for help regardless of whether you get a formal diagnosis, and make a big thing of the issues that you believe are the most important, providing written evidence of all the things that you see at home that they may not see in clinic to back you up.