[anyfoo]

The 80186 was completely compatible to its predecessor. It's just that there weren't many IBM-compatible PCs which featured an 80186.

[burfog]

The core was compatible, but it came with built-in non-standard peripherals. It had a DMA controller, interrupt controller, and timer. None of these were PC compatible.

[int_19h]

This particular one sounds like it has all of these, seeing how the webpage shows it running a bunch of DOS games.

[bitwize]

I think he only duplicated the 80186 core (which itself was a bit different from the 8086 core and had a few more instructions), without adding the peripherals that came on-die on an actual 80186.