"popular" isn't what the site claims. It claims this is at the emulation level, not game level. If I can't make my own rom and have it work, what it advertised is a lie.

It's an open source project, they aren't selling you anything. If you find it doesn't work as intended for a given ROM, you roll up your sleeves and fix it, ensuring the intended feature remains complete.

Or I guess one could just complain and nitpick on Hacker News.