As this article says, early in the process you often have several soirces of low quality, and all we can do is hope to get the best we can from anywhere we can. The name and versions of everything attached is fairly horrible entropy, but it doesn't hurt.
Also, total entropy is not necessarily the same thing as attacker's uncertainity of the pool's state. The difference seems mostly theoretical, but there are practical issues for both cases of these two quantities beeing wildy different.
Re: Entropy; in a system RNG design, entropy is typically considered relative to an attacker. In some very real sense, the "total entropy" of the system is only the unpredictability of the generator to the most knowledgeable attacker.