Author here: this is about as far as I can go. When chips get more than 1 metal layer, I don't have a good way to examine them. Professional reverse-engineering firms can go a lot further.

The furthest I've seen publicly is the original Playstation ASICs. http://psxdev.ru/ [Russian Language]

Similar in time to the playstation ASICs (and similar design in sort of a soup of standard cells on a CMOS process), but at a gate count similar to Ken's fantastic work here on the 8086 is the work reversing the Gameboy SoC: https://github.com/furrtek/DMG-CPU-Inside

Chip manufacturers, professional chip reversers, and academic institutions have the tooling to take chips apart at varying levels of granularity all the way down to atom by atom if necessary.

Nonw thats a good question, I'd love to see the Intel Management Engine circuitry and the AMD PSP circuitry, knowing its got an AMD cpu and AMD's give you infinite ways to return. https://news.ycombinator.com/item?id=34720416