Hand written assembly is pretty common in video, no matter what they say. All modern video codecs have hand written assembly for all modern SIMD extensions, even on ARM. They didn’t say anything about where these numbers come from. Likely compared against unoptimized C code. There will never be a case where having AVX-512 will give you that kind of speedup, because there will be fallbacks for more common extensions.
It has a display and even bluetooth. The Firmware is open source. The schematics are available.
Imo open source is not that important for an iron unless you want to add a klingon translation. But the iron is pretty good, although it is often rather >50 bucks including shipping.