Foot Block Rule Question

[Main Street]

We have the sight of players who can dive directly in front of the ball kicker, performing a fully stretched arm and face block directly against the kicker. When effectively carried out, the GAA world is giving the fearless defender a standing ovation, no mention of heath and safety.
But when the leg is used to block the ball regardless of minimal or non existent danger, the  GAA world screams Footblock!! 'One leg bad,  two arms good'