What does “Biden only” votes mean to you? Is that where you see vote totals jump for Biden, but not for any other candidate? Because your conclusion from that, that it’s obviously fraud, seems incredibly naive. The simple answer is they update candidate totals in chunks.
Further, if someone was committing fraud, they could just add a few votes for other candidates to evade your detection. Your sniff test doesn’t pass my sniff test.
Biden-only means the ballot is marked _only_ for Biden, and not for any of the congress or local legislature candidates. That's unlikely as fuck, especially when such ballots come as a large batch or a series of large batches. That's what you do if you bought into the "Joe is ahead by 15%" polls and didn't have the time to make your scam believable at 4AM on November 4th.
Further, if someone was committing fraud, they could just add a few votes for other candidates to evade your detection. Your sniff test doesn’t pass my sniff test.