The mod checks whether a recipe can be crafted. There should be no deadlocks. If you encounter one, please submit a bug report including the issue, the seed, and the list of installed mods.
In your case, the constant combinator is an ingredient for Assembler 1, but it can be hand-crafted and is therefore valid. Assembler technology is not mandatory for Circuit Network technology. It's a bit unfortunate, as you have to produce green science without assemblers, but it works as intended.
A toggle to group recipes by science is not feasible in the current codebase, as it would require a complete rewrite of the logic. Therefore, I will not be adding it.
