True, but only in our current understanding of flags. In medieval times, there were metaphors, but mostly heraldry and patterns to represent families so that you could figure out which branch of what family it was. Eventually, that became crests instead of just color/texture/patterns. In certain areas, color is tied to religion (e.g. the prevalence of green/red/black flags in the Middle East).

Cyprus has a literal map of Cyprus on their flag. Tuvulu’s flag has a star that represents each of the islands. Papua New Guinea’s shows the Southern Cross to indicate its location in the Southern Hemisphere and because it’s usually visible there.

In short: what I’m saying is that “the idea of flag design” has changed over time. Modern, Western flags are philosophical, but other regions in the world are spiritual… or technical… or literal (maps).

Also: as I wrote in my above comment, we don’t have to be literal with our flags because we all know what the Earth looks like. If the goal is to represent it to someone or something that has never seen Earth (and doesn’t know where it is), and approach like this has validity.