I tried to figure out if this was real, and the closest I found was this article where setting a solid color background in windows 7 would cause up to a 30sec delay during login. The solution was apparently to make a small image in the color you wanted, and tile that image so that it would cover the whole desktop.
Here’s a hackernews discussion on it, includes some other fun stories like how windows 95 progress bars would complete faster if you were wiggling the mouse the whole time.
That has nothing to do with single threading that shit, an Arduino could draw that image faster. Most likely something fails to start correctly and windows waits for a 30 second timeout to run out before continuing anyway.
Well yeah, the reply is obviously a joke. Displaying an image is a single threaded task regardless of the contents, and adding threads will just make it slower.