Not always. Steve wanted to, but Steve disagreed. For the Apple 2, the net effect was that it shipped with hardware schematics (everything, including the power supply) and commented ROM listings.

Even the original Mac still had fairly comprehensive documentation of parts of its hardware, if you bought the phone book edition of Inside Macintosh.

And of course, IBM didn't 'settle' for opening up the platform. Compaq and Phoenix Technologies opened it for them.