The biden only ballots were the test ballots the woman testified about at the GA hearing. She caught some traitors printing them at her workstation when they thought she was gone.

A test ballot has only one dot filled to calibrate that sensor for that dot. To calibrate the machine they print a separate ballot for each dot position and run them all through the machine. The riggers were only printing ballots with the biden dots filled in, and she thought they didn't know what they were doing and offered her help. She later realized what they were doing.