I don't think that suffices, because I have never heard European countries described as "undeveloped" (perhaps "underdeveloped"), if that. The benefit of the doubt usually orbits a common sentiment, and in this case there is a conspicuous incongruity.

As for the edit: "The test takers were self-selected." The tests also seem to be online-only, and by that measure, likely textual.

I'll say that there is an explanation for the phenomenon I've described: if one has the privilege to conduct business and socialize in one's native language, speaking proficiency in a lingua franca could likely be lower.