Your joke is on point. I think I was unclear.
There are many who are multilingual. If they grow up in a region where multiple languages are spoken, they will develop some proficiency in all of them. However, often, those languages are close linguistically, just as they are close geographically.
Those on the "polyglot" facebook group are self-identified polyglots. They have an interest in learning languages from different and varied language families. That group of people is not representative of hardly anyone in the world, the majority of whom speak only a single language or only several related languages.

On Tue, Jun 10, 2014 at 11:25 AM, Paul Bartlett <[log in to unmask]> wrote:
On 6/10/2014, Jeffrey Brown wrote:

But most of the world does not consist of polyglots.

On Tue, Jun 10, 2014 at 2:59 AM, Dmitry Ivanov
<000000333e3a2e5f-dmarc-[log in to unmask]
<mailto:000000333e3a2e5f-[log in to unmask]edu>> wrote:

      I'll give you a few examples that I have at hand to demonstrate
    that "worldlang" doesn't mean "unintelligible". From time to time
    they post a picture with a short text in Lidepla to the Facebook
    group of "Polyglots". Here are some reactions:

​[... snip ...]
I don't know about "most of the world," but there is an old joke: "What do you call someone who speaks three languages? Trilingual. What do you call someone who speaks two languages? Bilingual. What do you call someone who speaks only one language? An American."

Now of course, this is not literally true, as there are many Americans who have at least some competence in something in addition to English. However, it is so that for many generations in much of the USA, foreign language instruction simply was not available, and what little there was was optional and often not offered until age thirteen or fourteen at the beginning of high school. (That was my case.) And moreover, the quality of instruction was sometimes rather poor. (Mine was so-so.)

On the other hand, in some other parts of the world, either people "absorb" (figuratively speaking) a second (or more) language from their environment, or else they receive competent instruction at (relatively) young ages in formal education.

All this is so (I assert), but I do agree that there are huge numbers of people in the world who are not polyglots and for whom many conIALs would be mysterious at first sight.

Paul Bartlett