> That's an odd convoluted definition that I've never heard of before

It's a “definition” in the sense that it is a description semantically equivalent to what the phrase “dark side of the moon” has always referred to; it is not, however, a description of the etymology of the term, which derives instead from the long established use of “dark” to mean mysterious, hidden from knowledge, obscure, occult, etc.

In this case, silent side of the moon is more useful, since that's why it's so attractive to scientists.