Hey, you should check the bug report somebody made on my mod. https://github.com/LuziferSenpai/factorio-mods/issues/11

What do you mean by "does not account for default icon_size"? Base game icons don't have size declared either, and it still works.
In fact, I just enabled your mod, and it works, the productivity researches for extra casting recipes show up in the technology tree.

Weird, then the reporter missed a mod.

After some debugging, we determined that it seems to be a quirk of the game engine that has nothing to do with this mod. Closing this down.