Again, you need to remember what a slapdash document the format proposal was meant to be. It wasn't for publication; it was just something to hand out to network executives to support his verbal pitch for the show. It's riddled with typos and a lot of it is clearly handwaves and gibberish. He didn't specifically intend to make Spock half-Martian; he said "probably half-Martian" because he hadn't really given a lot of thought to the specifics yet and "Martian" was just the first thing anyone in the 1950s-60s thought of when they thought of creatures from outer space. This was a rough sketch of his ideas for Star Trek, nothing more. It's very unwise to read too much meaning into whatever random coincidences might crop up in it.
On that note, I was looking at screencaps from "The Menagerie" a while back and was amused by what the folder Kirk is shown actually says
, in relation to Mendez' description of Spock as the "half Vulcan science officer" who visited Talos.