Hola,
I’m a native Spanish speaker from Spain (I live in the U.S., spoke English all my life with a native English speaking father and my English could be better than my Spanish). Since I am Spanish, we use vosotros. While I heard people in the U.S. learn “ustedes comen”, I would say “vosotros coméis”.
I’ve been learning Spanish on my own and what I’ve learned agrees with what you stated.
Vosotros is a dialect of Spain, but it’s rarely used outside of Spain.