AVX2 is 256 bits wide, not 256 bytes.
That is unless Intel have done something amazingly customised for Amazon, but they'd have had to charge $quillions for it.
AVX2 actually pretty good. It finally has an instruction set on a par with (though still not quite as good as) Altivec found in the sort of PowerPC processor in an iMac G4. It illustrates just how much Intel have depended on ramping core speed and memory subsystem performance. That takes 100s of millions of transistors for all those caches, decoders and pipelines; expensive. They've neglected the more elegant but easier side of CPU design - the instruction set.