FWIW, IIUC the binning process that designates chips as Core, Xeon, Pentium etc series ultimately sources parts from a common set of conveyor belts, identifying final designations using QC processes that further subclassify against what parts of a chip do not work correctly. So if say the AVX512 unit in a single core doesn't pass muster an entire die might go in the "doesn't have AVX512" bin and then get marketed appropriately; or perhaps (uncited speculation) a chip that fails the test suite for a Xeon E3 might get rebranded as a Core i3 instead.
I do wonder what percentage of this classification process is driven by process yield and how much is driven by volume quota requirements. I wouldn't be surprised to learn that this is an area of careful optimization; for all I know the entire silicon portfolio just ships the process yield org chart.
But all this means the user-facing FLAGS in the chip under the keyboard I'm typing this comment on is the result of a fuse configuration (aka policy), rather than a 1:1 representation of the potential of the photomask, and there are very likely a few micrometers worth of functionality I'll never get to use.
Of course I'm very curious if this is because the disabled areas were faulty (optimal use of manufacturing potential) or because *shrug* The Manufacturing Computer needed to meet its quota of Core i5s that day (arguably optimal fulfillment of volume potential). (Then there's the argument of disabling feature X across all cores for consistency, hmph.) But this is all firmly out in the weeds of implementation minutiae, and way beyond reasonable optimization; I have no idea what's theoretically broken in my CPU - and whether re-enabling that functionality explicitly to torture-test stuff I might like to make resilient would present me a relevant surface area of functionality I even knew what to do with (haven't yet played with C intrinsics for example).
At the end of the day, disabling functionality on-chip seems to be one of the few viable ways to claw fabrication yield back to something commercially viable and not utterly eye-watering, and IIUC it's been a staple for a long time.
Rereading your comment I realize it's quite possible you were writing with some or all of the above context implied and I may have misread. Not sure, disregard if so.