18a-p was supposed to be the first process totally designed to be compliant with standard PDK rules, so a bit surprising that the shift is not to that (as expected), but 14A has for some time been considered the first fully compliant offering.
The difference is in the design rules, which Intel had optimized for CPU. Many details of this are out there for anyone interested, and it looks to me that the variation from what TSMC or Samsung offer were not meaningful in performance. Just another example of the Product + TD coming up with a solution that served no purpose beyond increasing complexity.
Although it is important to grow external WSPW, to enable the fabs to scale, it is also important to shed all of the needless complexity which infested the IDM model, and simply do business like the rest of the industry.
As with everything else, LBT seems to be making that shift, with some urgency.