answer
salam alikoum,
my answer was taken from a passage written by sheikh yousuf estes, he said that revert is most suitable when descrbing someone who is returning to its original state (elfitra)
and convert is to describe the transition from something to something else.
when we deal with new muslims, we call them reverts, because allah created them on fitra, and they are back to it.
and allah knows best.
wa salam alikoum