like I said in other posts, your casted vote is anonymous but not your ballot packet. when you cast a vote into the system, it can't be traced to you. so nobody can say I want a list of all the people who voted for Biden. but if you drop your ballot packet outside the polling location, polling officials can look you up on the voter poll registration book and identify that packet belongs to you. most places only anonymize your data when they separate the ballot from the envelope it's enclosed in. usually before that, there is an id matched to your ballot packet to your voter registration. some counties vet ballots prior to separating ballots from packets. this is mostly done for checking intent and that there aren't weird shit in there (a lot of people stuff gifts and stuff into their envelopes) before being sent off for tallying.