Inside Macintosh was great documentation (I’d argue that the second generation in the 1990s, split up by topics, was the peak of Apple’s documentation writing), but I would not classify it as “Internals” in the sense of how a 1970s computer would be documented. There was a clearly delineated API boundary beyond which it was discouraged to venture.
Yes, Apple was/is mostly about computing as an appliance (realized fully in iOS), but there was occasional dabbling with User computing, especially with HyperCard, and to some extent with AppleScript. It seems that ultimately these did not have enough uptake to warrant investing more into them.
The more time I spend getting elderly people’s entertainment systems back into a state where they can watch their 3 favorite TV channels in peace without getting lured into the paywalls of their Android TVs or cable providers, the more sympathetic I’m getting to the “appliance” view.
I used that name because I did not recall exactly the naming and was too lazy to search for the actual one. :)
Something like Hypercard naturally allowed for experimentation and playground, and if anything, a proof how to balance programming in the context of appliances.
You can find something more recent like Dreams for the PlayStation, which is also no longer.
The difference is that even environments like HyperCard and now all the sandboxed stuff create a clear division between mere "power users" and "developers", while the PC had a ROM BASIC in the beginning that effectively gave you full access to the hardware. DOS came with DEBUG that you could write short binaries in, and PC magazines would often publish source code for such utilities. These were no less lacking in power than any other software. With a PC, there was no sharp division between user and developer.
Their vision after Lisa and Macintosh has always been computing as an appliance.
The only thing open about them were the great Macintosh Internals books, that Apple documentation team has forgotten how to write.