I've done something similar for a refactor.
It simply forgets code exists during a port. It will port part of a function and ignore the rest, it will scan a whole file into context and then forget that a different codepath exists.
I would never rely on it for a 1:1 mapping of large features/code transformations. Small stuff sure, but beyond say a few large files it will miss things and you will be scratching your head for why it's not working.