Apparently the Israeli chief rabbi has convinced some of his American rabbinical counterparts that only he, Rabbi Amar, knows the correct magical incantations that can transform a Goy into a Jew.
Only he, Rabbi Amar, knows how to evaluate the sincerity of a convert. Only he, Rabbi Amar, knows the secret standards that must be applied so that the magic of conversion will take effect.
It's either that explanation - or it could be that the Israeli chief rabbi has successfully bullied his American counterparts into political submission. ("One US rabbi who supported the agreement said that it was legitimate for the Chief Rabbinate to demand minimum standards for conversions." Only they know the secret incantation and handshake.)
He dresses like the High Priest of the ancient Temple. Only he can declare who can come into the sanctuary of the Lord.