Look up the Texas Instruments am3358. It's a tiny SOC, it was used in the beaglebone black. Its technical reference manual[1] is over 5000 pages, and it details all peripherals, all of the interconnects and every single register in the system. This, by contrast, is really just an overview.

Regards to (1), if you don't publish this information you're not selling a CPU, you're selling a very expensive chunk of sand. There is simply no way that a customer can guess at what your implementation looks like. Additionally, Intel barely has IP in the traditional sense. They hold patents, but their only real competitor in making x86 processors, AMD, has a long-standing mutual non-enforcement agreement wrt patents.

Regards to (2), I'm guessing a majority of this PDF can be generated sort of like you generate API documentation from doxygen comments.

[1]: https://www.ti.com/lit/ug/spruh73q/spruh73q.pdf?ts=175651560...

I worked on a similar TI SoC -- with War-and-Peace-sized datasheet. My eyes burned out and brain exploded. Ultimately, another engineer had to take over the project -- or rather TEAM of engineers, of which I did only a part. It's simply to much complexity to expect one engineer to grok it all, do the schematic & PCB & power supply & hi-speed MIPI connections and radios and... and THEN to write the software for it all. It's too much. (This is the Life one gets in Startups, it seems -- worked to the (beagle)bone!)

having used the AM3358 extensively, the TRM is not complete. There are some pretty important and complex systems that have literally no documentation at all in the TRM, not to mention the large number of quirks and small details that you can only pick up from a scattering of other areas (including a wiki that TI deleted some years ago). It is, however, miles better than the documentation available for most SOCs.