Anthropic almost certainly also has optimized software down to the assembly level, considering this take-home interview challenge they published: https://github.com/anthropics/original_performance_takehome/... which is all about instruction-level performance optimizations. That they don't prioritize UI fixes just means they consider other things more important.

Unlikely: that product is written completely by AI, of which they are not lacking.

More likely is that an AI generated codename is impossible to fix by humans, and SOTA was not able to figure it out until now.

that's pretty silly to use as a measure of what they do internally