My son is mid to high functioning ASD. Our OT had told us the same things. We never used the manipulatives for HWT. And tbh I didn't realize there were manipulitives. My sons biggest problem was holding the pencil wrong. I CNT even explain it, I guess in a way he held it as you explained. When we did our writing he had to hold the pencil correctly and when doing assignments. It was a constant trouble. He could hold pencil how he wanted when drawing...a yr later(Now) he finally holds the pencil correctly all the time. He's 11 btw. Just wanted to share our story with you.