This has nothing to do with compression. If you use "yes" and "no" instead of "oui" and "non" (which just happen to be three characters each) and you compress "yes" to "T" and "no" to "F" then the uncompressed text will be the leaky one.
Yes, and my example was an example meant to prove the opposite idea. The point is that it is irrelevant whether you compress or not. You can leak information either way.
It's in the article if you would bother to read it LOL. "simply measuring the size of packets without decoding them can identify whole words and phrases with a high rate of accuracy . . . [the researchers] can search for chosen phrases within the encrypted data"