This is likely a misunderstanding or a fabrication.
Here's why this claim is untrue:
* No cultural basis: There's no evidence of such a practice in French culture or folklore.
* Frog legs are a delicacy: While frog legs are eaten as a delicacy in some parts of France, it's not linked to romantic rituals.
* Love potions are a myth: The idea of eating specific foods to attract love is a fictional trope, not a real practice.
It's important to be critical of information and check its validity, especially when it seems strange or unusual.