All the G4 PowerBooks I remember used mini-DVI?
https://en.wikipedia.org/wiki/Mini-DVI
Which is cool, but not quite as cool as micro-DVI, which they used for exactly one MacBook Air generation before mini-DisplayPort arrived on the scene
https://en.wikipedia.org/wiki/Micro-DVI
Edit: you are right though. I just pulled up pictures on early G4 variants, and there is indeed full-size DVI. I completely forgot that.