> Given that The Hobbit was not actually intended to be connected directly to his Middle-earth works except retroactively

In the first version of the book I read, there was an offhand mention that a Took ancestor had married a "Fairy" (or Fae). It was never discussed in the book again and I found that later versions had it charged to "Elf".

I always supposed that this was another bit left over from the time where the Hobbit was its own universe - at least I never heard any mention of Fairies living in Middle-Earth.

Edit: Of course maybe a wiser choice might have been to leave it in - and present it as a sign that there are still a lot of unexplored corners in Middle-Earth and even after reading all the books, we don't know all about it.

I think the modern pressure to have a "canon" which explains absolutely everything that goes on in the world can lead to sterile and unbelievable worlds as well if a worldbuilder gives in too much.