In those waters it might be more dangerous not to.
I can't find a "still photo"anyone got one?
I believe he is asserting that the boats were certainly Iranian, the radio call could have been “anyone”.
I suppose that Farsi and Arabic, being linguistically unrelated, are different enough that a skilled linguist could disguinish the difference between an Iranian accent and an Arab? Like the difference between a Chinese and Japanese accent. [Not to be racist, but Chinese: “flied lice”, they pronounce “r” like “l”, while Japanese pronounce “l” like “r”.]
Even if the voice were Iranian, it might be someone other than the Iranian navy.