The official name of this site is "TeX - LaTeX", which is written with a hyphen at most places, this is obviously incorrect. I understand that in a page <title>, this is a common practice in HTML. But I think it could be corrected in the text/body of the About page, and the en-dashes – put there. If I didn't oversee anything, it is 4 times in that page.
Related questions (this will help with keeping everything consistent and preventing misinformation):
Outside of formal writing, I don't think think the careful distinctions between the use of hyphens and kinds of dash really apply, and even in formal writing, in this case I don't think you will find much in the way of clear guidance at all from style guides: here the equivalent of a running head is formed from a category (tag) and a title, a case where I think Chicago offers no sharp rules, and uses a colon for the task (see, e.g., 16th, p.843). So I disagree that it "is obviously incorrect".
A purely pragmatic consideration against the change: dashes are larger than hyphens, and space is typically at a premium in browser tabs. We would see a tiny little bit less of the title when we have many browser tabs open.
