In the books, and movie iirc, they used DNA from all three, not just frogs, to replace missing segments of the dino DNA.
It was just that Dr.Grant guessed at it being amphibian DNA that had the unintentional side effect of allowing some of the dinos to change sex (which is a thing called sequential hermaphroditism) when he finds the velociraptor eggs.
In the books, and movie iirc, they used DNA from all three, not just frogs, to replace missing segments of the dino DNA.
It was just that Dr.Grant guessed at it being amphibian DNA that had the unintentional side effect of allowing some of the dinos to change sex (which is a thing called sequential hermaphroditism) when he finds the velociraptor eggs.