In many cases a provisional voter is one who is legally registered to vote but goes to the wrong precinct and therefore doesn’t show up in those voter records. They don’t have to visit every one of these people to verify where they live. They just take a ballot from a person who lives in Precinct A and voted in Precinct B, and verify that they are legally registered in Precinct A.
However Dems have been successful in preventing regular attempts to "clean up" voter rolls. I would guess in urban areas such as Philly, voter rolls have not been cleaned up for decades. Much fraud is perpetrated by persons impersonating legally-registered voters ... who in fact are long gone.
That's why a more rigorous investigation needs to be done for this kind of provisional ballot. But in Philly, is a thorough check ever done?
In our area of New Mexico, precinct only matters for local races (i.e. city or county races). Your name and precinct are in the computer which is county wide so you can vote at any one of several convenience locations. When you check in, they print a ballot relevant to your precinct, you darken your candidate choice and insert it into a machine. Of course the paper ballots are available for a hand recount if necessary.
My neighbor told me that at her voting location a Hispanic woman who didn't speak much English tried to vote but was not registered. She was told very politely she couldn't this time, but she was given a voter registration card and informed if she filled it out, she could vote next time.
But we are a Republican area; if we were a Democrate location, they very likely would have given her a ballot anyway.