Portable only to certain extent, the moment you start junggling extensions it could be a complete different API for all pratical purposes, depending on how much extensions one needs to take care of, and the different semantics across them, or similar extensions from different vendors.
Also, OpenGL never really quite made it into game consoles, only in some ways not fully compatible, so if they are a target, one already needs to handle multiple APIs anyway.
Also, OpenGL never really quite made it into game consoles, only in some ways not fully compatible, so if they are a target, one already needs to handle multiple APIs anyway.