But who are "US Latino adults" to begin with? This kind of statistic is based on an egregious confusion between ethnicity and citizenship, familiarity with languages, "communities" and subcultures. Labeling people (particularly other people) is problematic in itself.

"Latinx" is a sophisticated word from and for sophisticated people (such as the mentioned LGBT activists, who are often ready to adopt neutral replacements of masculine and feminine words); its usage should be considered an indicator of such sophistication (do you find it proper or silly?) and social contexts (who would you call "Latinx"? What would they think of you if you did?), all quite orthogonal to people's identity.