Echolalia is a typical Autistic trait for children to speak when they become verbal. I wouldn’t discourage it out of concern he might regress.

It is a phase. Some grow out of it quicker and some longer. Normal-developed children go through this stage as well. How is his receptive language level? My son repeats questions he doesn't know how to answer. He has MERLD. You can model the correct way to answer for him and teach him more vocabulary. That's what my speech therapist told me.

Our son is the same way. He knows he has to be good at the store or he loses tv privileges when he gets home. Some days it's worse than others.