I understand what they mean, but that does not make it right. I actually like uzbl, but it is neither lightweight, nor does it follow the "Unix philosophy". By their standards, you could say that MS Word follows the Unix philosophy because, well, it does only one thing (editing texts) and some even say it does a good job at it.
Yes, I am exaggerating, but an important aspect of the "Unix philosophy" is that this "one thing" a tool does should not be easily decomposable. For instance, 'cat' does actually several things (it opens a file, reads a stream, outputs it, closes the file, etc.), but it wouldn't make sense to decompose it further. "Rendering a webpage" is not one simple task, but requires hundreds of steps which actually could be splitted into separate tools. Now, such a toolset, which separately deals with stuff like ECMAscript, CSS, HTML,etc., that would interest me very much.