There is a strong advantage to a homogenous ISA. I am glad to see that newer chips have more full support of these instructions. Maybe they are still emulating

There is a strong advantage to a homogenous ISA. I am glad to see that newer chips have more full support of these instructions. Maybe they are still emulating them with micro-ops without real acceleration still convenient. Regarding the mobile lineup and AVx2, honestly I wouldn't know. It is very much possible that they disabled it to avoid competing with higher lineups. But a more likely (IMO) reason is that to add 256 bit support added enough costs that the were either unacceptable or simply aren't justified by target workloads when evaluated in simulations. The physical reasons I was alluding to revolve around power, area, and capacitance (delay). These inform the cost ($$$) and performance of chips. Some of these big features (like AVX3) push the limits of what you can do without having to use high performance transistors or deal with intense power draws. Another physical reason is that sometime parts suffer effects during manufacturing. Modern design of chips is inherently modular, so sometimes the only option is to disable certain parts of the chip.