Misleading preflight check for rich black text and searching for K<100% text

I'm afraid that the Preflight check Text uses Rich Black in Acrobat misidentifies K=100 text as "Rich Black", although in my case C=0, M=0 and Y=0. This may mislead you into believing that there's something wrong with your document (in cases when you don't want any rich black text). At least that's my experience. So the question is am I right about this or am I missing or confusing something?

You can try it yourself: just run this check on some document or create a new one in Indesign. It can be just a single white page with some text on it in default black (it can be just one word or even just one character).

This preflight check is described in Acrobat as: "Text Objects are using Black and at least one of the Cyan, Magenta and Yellow channels is not zero". I clicked "edit" there and from what I saw there it seems that the factory settings for this check are wrong or something (I've never changed them). Please take a look at it and tell me am I correct.

I needed this to check whether I have some rich black in my text. Previously, Indesign's preflight caught some instances where C, M or Y plates were used, like some words or characters here and there. I fixed that, but just for the case I wanted to doublecheck that in Acrobat as well.

And one more (related) question: how to search for a black text that is less than 100%? In this case the CMY plates are not used. This text might be dark gray or something, so you can't notice it so easily.

Thanks for your advices and opinions