Description of Locative 2 in "House" section
In the "House" section, the reminder for Loc2 is somewhat lacking. There's no mention of Type III nouns with Loc2, but more importantly, it's also plainly false that Loc2 is obligatory. While снег and лес very nearly require it, it's still not licensed (AFAIK) in a sentence like "There's much beauty in a forest", when talking about forests as an abstract thing. Other nouns, like край, prefer Loc2 in certain idiomatic contexts, and some nouns only allow Loc2 in very specific idioms. There's also a number of items that allow Loc2 to varying extents, and indeed I think this is the more usual behavior for Loc2.
This situation is also fairly new, so with older literature (and some older/much more conservative speakers), Loc1 and Loc2 are much more likely to both show up with the same noun.
See Timberlake's discussion (starting p 330) for a detailed discussion.
This is a basic course, they mentioned it just to make people aware of its existence, so they don't think that they're seeing a novel application of dative.