AMD's Tricore vs Quadcore... something (I think Phentoms??) were definitely this. Some Tricores were able to turn into quad-cores with some firmware hacking.
The IBM-Cell in the PS3 was a different approach to the same problem. The Cell was specified as 7-SPUs and 1-CPU, but in actuality... the manufacturing process made 8-SPUs and 1-CPU.
IBM assumed that one of the SPUs would fail during manufacturing, so they only promised to deliver 7 of them per PS3.
You can literally see the 8 SPUs: https://upload.wikimedia.org/wikipedia/commons/e/e0/Cell-Pro...
There's lots of ways to approach the problem. Manufacturing is an imperfect process: not everything is made identically. So the manufacturers have to figure out how to test for differences and... if necessary... sell the same "manufactured" chip in different bins.