Suggestions to use motor assessments within the diagnosis process have existed for the better part of the last two decades, though people have rightly cautioned its inclusion within the diagnostic criteria (though there have been recent calls to revisit this idea).
In my perspective, motor skill can be a good indicator for early diagnosis (e.g., motor delays appear earlier than social ones) but should not be considered in the diagnosis as there are many conflicting reports of delays and too much overlap with other behavior or developmental disabilities. Additionally, as I and others have argued, there’s little to no evidence suggesting that motor impairment is entirely indicative of the presence of autism; for instance, are delays related to coordination that is impact through neural pathways influenced by autism or is it that autistic kids learn early motor skills differently due to attention, imitation, or limited exposure.