I presume they know who submitted the ballot not how they voted. That way they can check them off the list in case the person tries to vote again on election day (likely only works in Pubbie states; Rat state election officials probably welcome multiple votes).
I did some checking to see if my ballot was received and it was The SOS site also said, “counted.” Not sure if that means my vote has been cast in the Trump column or if the ballot was marked as received????