Barring Quenya-ripoffs and the Keyes stuff I forgot about, none of those languages have much the way of actual phrases and grammar, do they? I didn't mean that all Tamriel speaks two languages, of course.
Ayleid is pretty damn compete, as is Yoku (much of which I've yet to add to the dictionary - oops). Ta'agra is too complex to decipher grammar out of, but we have a fairly comprehensive sample and know some of the rules from the developer who designed it. Between Ehlnofex, Aldmeri, Dunmeri, and Kothri, we have a good grasp of the form and function of Aldmeri-derived languages. Thats hardly "no in-game languages exist."
I've never seen anything as complex as the babble in the OP.
Thats cause a bunch of TR people sat down and wrote a huge dictionary and grammar guide back in the day. I'm quite frankly surprised that quest is still in the mod, since we've since decided that the language is not very good or accurate.