Komamura didn't say anything, I mixed up between both of them, Iba said Bankai first then he said true power (which is Bankai), Komamura just overheard their conversation and pretended he didn't hear anything. (by saying my ears aren't working) So yea, basically both knew, if these 2 knew then others might've known about it too, though Mayuri knowing about it is because he's the one who's responsible for these Zanpakuto-related things.