Title, pretty much. They all seem to be under the same tab:

I'm not familiar with the recipe book. So I have no clue what I'm looking at.

I'm not sure what to answer. It's the vanilla recipe book, which is basically a very basic "creative tabs" for survival, transfering recipes to the crafting grid when you click on them.

//e: seems like the standard tab to go in is "misc" (as shown in the screenshots) for recipes that don't have a defined category.

I'm not familiar with the code behind the inner workings of the recipe book. Or any code, for that matter.

//e: from the wiki:

The first, topmost tab contains every unlocked recipe.
The second tab contains tools, weapons, and armor.
The third tab contains building materials.
The fourth tab contains food items and miscellaneous things.
The fifth tab contains redstone materials.

Also, Quark seems to sort blocks & items correctly (not all of them though, and I've opened an issue on their end regarding this).

So the categories in the recipe book gets its content based on the Creative Tabs?

After looking into it a bit, I've discovered the following:
The Recipe Book tabs contains the same items/blocks as the creative tabs. For the Creative Tabs that does not match the 3 defined one is all thrown into "Misc"
Atum have its own Creative Tab with all its items/blocks, which is why it's thrown into "Misc" in the recipe book.
As mentioned here MinecraftForge/MinecraftForge#4601 , there is no way to change this in Forge atm.

Oh boy. Thanks for looking into it.