Pretty sure "That man" is Linus Torvalds and the light bleed is actually the desktop background (looks like a photo)

As for the rest.. 🤷

Why is "ios" the only one not in all-caps?

iOS begins with a lower-case 'i', making this error more frequent.

Why does the apple hq list their mobile system while the other two list their desktop/workstation/server systems?

Apple's most iconic product is the iPhone, but the meme compares software. So the 'Apple'-item then becomes iOS.

Why does each get a different proportion of the screen/why aren't they equally sized/why are they not stacked vertically?

The rule of three applies to jokes and typically dictates that the punchline is third and given extra emphasis. The layout reflects that tradition.

Why is this man not using dark mode, and how is the obvious and glaring light bleed at the bottom-left of his monitor just get accepted?

From what I've seen, Linus Thorvalds uses default work environments and doesn't care much about hardware beyond functionality.

This picture, it frustrates me on many levels.

Why don’t you tell us about it?

And the weird-ass border probably due to the piss poor crop job (why not save the image instead of taking a screenshot?). I don’t know how people live like this.