It can be a bit dodgy. Warg Fangs in particular are bad about unlocking their extract. I've had two playthroughs that necessitated manual extraction to unlock the recipe as even extract all wasn't picking them up.

but I think the recipes become available once you have the extract necessary.

Yes, you've restated the title of my post.

As far I know, the only way to discover that was to make extracts for recipes I didn't already have, but there was no obvious reason to do that, since I had no recipes that could use them.

(Some people might argue here that making the extracts saves weight. True, but not everyone hoards enough junk to need that small weight reduction.)

Meanwhile, the game offers recipes written down in the world, so it was easy to assume that we're supposed to discover them through exploration.