I didn't think these motors had those either.

Pretty sure only the black motors have cats. Anything Merc Racing does is exempt. Even the 520's have the 496-style manifolds/risers on them with no cats.

I think that's a misleading video, and the angle is bad to get good sound from the transom. The audio quality is terrible period, almost like someone had their finger over the mic. That may be a Go-Pro video as well, which they don't have the best sound recording. That, and the transom is pointed away with twin bustles, aiming all sound waves in the opposite direction, as well as there is nothing behind the boat to bounce the sound off of.

My Go Pro captures sound just fine. The turbos kill the sound.

Sometimes I wish mine was that quiet. (eh not really)