This happened in Roanoke, which is left leaning. Republicans are going all out to cheat in this election.
Edit: Here is the law on tampering with ballots in Virginia. Class 5 felony
https://law.lis.virginia.gov/vacode/title24.2/chapter10/section24.2-1009/
I could be mistaken, but most places check your signature against the voter roll. If your signature doesn’t match, then they’ll ask for an ID. At least that’s how it was where I volunteered in 2020. This is done before you get your ballot. You don’t actually sign the ballot itself.