[VancouverMan]

A nuance of that usage of "guys" to refer to a group consisting of both men and women is that the group of people being referred to is typically immediately present in some way.

Like in those earlier examples, the people are probably all within the same house/yard at the same time when they're called to dinner, or they're all using the same online discussion forum at about the same time.

When discussing multiple individuals with significant time and/or distance separating them (like the people somebody has dated over the span of years), a more specific term like "men", "women", "men and women", or "people" would likely be used instead.