Am I completely misreading this? Theoretically this is not only rent seeking but also ability for cloud provides to be able to configure the same piece of silicon with different features based on demand / etc.
Why disable half the cores and leave them unsold, when selling both halves makes you twice as much money?
This allows for upgrades without having to replace the hardware. Consider you buy consumer gear at consumer prices without ECC functionality. Then you decide you'd like to run ZFS or something where ECC is encouraged. Instead of having to replace the processor, you just upgrade the microcode.