Saying it's an urban legend implies it's false, but that's a bit nitpicky IMO. Most people can read most such "scrambled" sentences without a lot of effort, so that part is certainly true (and non-obvious). The original - fact checked in your sources - made don't strong assumptions like "Cambridge researchers", "can be a total mess (...) read without a problem" etc. But overall I still think that's a neat fact.
Your links suggest that the attribution of the discovery of this phenomenon to a Cambridge researcher is an urban legend. But l33tman's comment doesn't make that claim, he only says that words scrambled in this way are easy to read (and they are, I read his comment effortlessly.)