They actually discussed that as a possible source of error.
It didn’t amount to anything unless god intervened with a miracle to make the chromosomes “doubled or tripled” and replicating vast complexities. It was considered an “over the top” concern.
The best they could do was conclude: If there was a 2-person bottleneck on the other side of 700,000 years… nobody would be able to prove there wasn’t because at 700,000 years ago… there’s too much noise to notice a 2 person bottleneck.