[Citation Required]

You could read it, it's pretty short.

Here's what the AUP says about porn:

You may not use any of Mozilla’s services to:

• ...
• Upload, download, transmit, display, or grant access to content that includes graphic depictions of sexuality or violence,
• ...

So yeah, in that sense it "says what it says about porn." It's just that "what it says about porn" is in a list of things you can't use their services for and before the only mention of how to use their "product."

Through their various agreements and terms Mozilla makes a clear distinction between products and services and has clear guidelines on how you can use them. When the TOS says "obey the AUP" and the AUP says "don't use our services for porn and don't sell our products or services" then viewing porn with their product is not a violation of their AUP and thus not a violation of their TOS.

Ultimately, however, the final decision would have to be resolved in court.