I'm unsure what those terms mean. What are qualities that perfect code or perfect understanding would have?
Depending on your framing I may agree or disagree.
Just to lob a softball, I'm sure there are/were people that have a perfect understanding of an older CPU architecture; or an entire system architecture's worth of perfect understanding that gave us spacecraft with hardware and firmware that still works and can be updated (out of the planetary solar system?), or Linux.
These are softballs for framing because they're just what I could type off the cuff.
To answer your softball, no, I doubt there was anyone who understood everything except petty early on. But very few people understand the whole OS let alone do any specialized task like data analysis, HPC, programming languages, encryption, or anything else. But here's the thing, the extra knowledge never hurts. It almost always helps, but certain knowledge is more generally helpful than others. Especially if we're talking memory but things like caching, {S,M}I{S,M}D, some bash, and some assembly go A LONG way