"analog" /"mixed-signal" Terminology confusion about the definition of some components and systems
Grouping is usually done for the convenience of someone that is trying to sort a large list of varied items into smaller lists that are easier to navigate. Unfortunately one persons idea of what belongs in what list is often questionable just like in the case of "analog" versus "mixed signal" 1. 

I have searched many times on a manufacturer or vendor web site for some type of part and not finding it by scanning through some category list and not finding what I wanted. So rather than trying to find that way I have resorted using web sites that have exceptional search features (both Digikey and Mouser are pretty good; some manufacturer sites are really bad). This way I can input parameters related to what I want and let the search engine scan the whole database instead of a category focus.

A simple example is if I am looking for capacitors on Mouser I would enter something like "330uF 16V" into their top search bar.

1 - I am reminded of the old saying that "everything is analog" in the big picture.