They write both. They write x86 repeatedly in the article and title, then show an instruction matrix that doesn't include, for example, the 468 CMPXCHG instructions or the crypto extensions PCLMULHQHQDQ instruction. Best I can guess, they mean 8086, which they think is equivalent to x86

> What you're seeing above is a C program that was compiled using GCC into native 8086 machine code being executed fully within CSS.

They did write 8086 in the text, but x86 in the title.