Pokedex Sorting Question

So... for a whlie now I've always wondered why the "Hide Incomplete" part of the Pokedex even exists. It doesn't do anything to really help in the way I would like to use it. Yes it does hide the incomplete dexes, but for example if I ONLY want to see egg dexes, why doesn't the "Hide Incomplete Egg Dexes" not remove all pokemon that DON'T hatch from an egg? It works just fine in the "Hide Complete Egg Dex", but the other option just feels completely useless. I would really like to use it to help me figure out what pokemon types I can hatch from eggs. Yes, I could always look at the type race tables, but when I have my own tool in front of me I'd rather use that.