Hearing the commandment

In the Shabbat 277. It is explained in the Responsorial Psalm that only Miriam was stricken because she began speaking first. Although Aaron was rebuked, it ultimately appears that the main prohibition is to begin speaking in the morning, as is the interpretation of the verse, "And behold, Miriam was leprous as snow."
My question is why they equated the speaker and the listener in the prohibition of the Shohar, since from this it is proven that the listener, even if he participates in the Shohar, as long as he does not initiate it, is only subject to reprimand.