It's because console development is a fairly secretive process. The SDKs are all kept under a fairly tight lid, and unless you either work with it yourself or personally know someone who is willing to spill the beans, you cannot get a good idea of the process.
True, but that is no reason to start spreading the falsehood that OpenGL is everywhere used on consoles, as many FOSS advocates do.
Specially when enough information is actually publicly available for anyone that cares about game development, in online forums, games magazines, conferences and game courses.
To be fair, the reason I though the Wii supported OpenGL was because that's what I thought I read from Nintendo when I was seriously considering writing some homebrew games for my Wii.
As to why and where I gained this misinformation I don't know. But somewhere along the line I've gotten my wires crossed.
With the game programming being secretive and so many people only being able to discuss it anonymously there should be a way to separate insiders from people who like to pretend to be one on the internet. "PS2/3/4 OpenGL" is one shibboleth we can use for this purpose.