Yes, they're supposed to copy ballots over. This is supposed to happen under close watch of observers that represent both sides, to make sure the transcription is accurate to the original ballot. When they fuck up, a ballot gets challenged and set aside for further review and manual entry.
Who are the types of people attracted to these jobs? We're talking temps, the kind of people that don't already have a 9-5. Young people with heads full of mush. The very kinds of people motivated to bring socialism and ruin the the United States.
When observers are kicked out, or the China Virus is being used excuse to keep observers so far away that they can't see the original and the copy, they're free to fill out the "copies" any way they want. We have no way to know the replacements are being copied accurately. Consider that people like this are the kinds of people filling these things out.
If he could get away with it, he'd count them all for his candidate.
The sad part is that there are so many different videos of people filling in ballots with no obvious reference that I don't even know which specific video you're referring to.