It's the same as "muppies" aka guppy mollies. Apparently people HAVE bred them.... Although there are rumors of it being true, there is no stated true fact, or experiment that says "yes, it is true!" They are completely different species.
As for platys and swords, yes. But... Guppies and platys? no.
Although they basically cannot successfully breed, it won't stop the males
Most male livebearers try to mate with any female livebearer...of his own kind or not! I had a little endler who loved loved LOVED my balloon molly Mama