> As mentioned in the quote introing this section, the Dwarves are explicitly described as mining coal in The Hobbit.
This is one of the key places where The Hobbit is unavoidably discontinuous with LOTR. Bilbo also has matches and a clock. Tolkien considered a larger revision of The Hobbit to bring it in line with LOTR but ended up only significantly reworking "Puzzles In The Dark", the chapter where Bilbo meets Gollum and obtains the ring. (Apparently the first edition also had a reference to tomatoes, which were replaced with pickles.) I don't think it's a strong basis for any arguments about the worldbuilding of Middle-earth.
This is one of the key places where The Hobbit is unavoidably discontinuous with LOTR. Bilbo also has matches and a clock. Tolkien considered a larger revision of The Hobbit to bring it in line with LOTR but ended up only significantly reworking "Puzzles In The Dark", the chapter where Bilbo meets Gollum and obtains the ring. (Apparently the first edition also had a reference to tomatoes, which were replaced with pickles.) I don't think it's a strong basis for any arguments about the worldbuilding of Middle-earth.