He or she meant by population I would assume. Approximately 5 vs. 10 million.

Population isn't very relevant when we're speaking specifically of things that relate to land area like topological maps.

But we aren't speaking of land area, we're speaking of buildings, which relate to population. I'd wager that LA County has more buildings than Finland.

But we are talking about building footprints which DO directly correlate to population, not overall area of an entity. So it's the most relevant factor.

Not really

Arizona and Croatia have the same population, but look at the aerial maps...

Right. If one interpretation is wildly wrong and there is another blindingly obvious interpretation that is correct and relevant... Why would we ever give someone the benefit of the doubt?

Or refer to the community guideline:

Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith.

Which can be found here: https://news.ycombinator.com/newsguidelines.html

Exactly. I would assume that the higher the population, the more buildings present. Just because you have a lot of land doesn't mean you have a lot of buildings.

Most of the building are not residential