Your link says
> Noting the obscurity of its 1982 release, BYTE in January 1983 called the System 9000 "IBM's 'Secret' Computer"
A computer that is not advertised is not going to win.
I think it was interesting that another bit of the company did use the CPU that it is often said IBM didn't use, or similar statements. It did.
Why the PC was promoted and the 9K wasn't, I don't know. Possibly price.
IBM later used modified 68000s in the S360 compatility card for the IBM PC as well.
Your link says
> Noting the obscurity of its 1982 release, BYTE in January 1983 called the System 9000 "IBM's 'Secret' Computer"
A computer that is not advertised is not going to win.