When people say "high settings," I almost always assume the intention is 1080p. That's probably not the best assumption, but when you can get a 1080p for dirt cheap nowadays... It's not altogether an unsafe one.
True though, you can play the game at manageable framerates at sub-1080p resolution.
Like vrumor said - some people can't "Just try it themselves" and don't want to piss away money when they realize it doesn't work and they should have saved up for something better. Also, we do look at benchmarks before we make recommendations, but truth be told is, most benchmarks don't consider less than 1080p these days because it's easily the most common resolution on desktops these days.