I looked into this and here's their reasoning: right now what they are doing is a statistical audit. Normally in these situations they hand count a small percentage of the votes to see if they match the machine tallies, and if the numbers are within a reasonable range of accuracy, then they assume the original machine count was accurate and call it a day.

This time around, they decided to just recount the whole batch by hand, because in order to achieve the level of statistical certainty necessary to verify an election is closed you have to recount a ton of us anyway. In the event that the hand count is statistically close enough that the machines can be trusted, they defer back to the machine vote, because assuming the machine is not rigged, it will more likely be accurate then hand counting votes.

If however, the difference is large enough to actually flip the election, that would indicate a high probability of fraud and I don't know what happens from there, but I guarantee it won't be certified for Biden in that case.

By the way Trump could still call for a recount even after the election is certified, but that would just be using the machines and it would be pointless. I still have not found a reason why they are not looking at the mail-in ballot envelopes themselves.

In any event, assume there are no weak links in the chain of custody, if the hand recount comes out close to the machine count, that would mean that Dominion voting machines were probably not fraudulently used in the election. But again that assumes a solid chain of custody. It does no good to do careful hand counts if some government antifa dude decides to enter in data which is close to the original fraudulent count in the first place. The entire process needs to be scrutinized very closely.