I have a somewhat similar feeling. Why has favicon.ico been made into a 10 page mess? It just feels like there's too much going on for something that should be so simple.
99% of people can just ensure /favicon.ico exists in their root and be done with it.
But with anything that can be done, it's nice to have a reference sheet for
how to do it well, how to do it right, and how to handle all the idiosyncrasies that exist on which clients like how to get the iPhone to grab the highest quality icon available when users add it to their homescreen.
You have an interesting definition of “non functional” describing a UI component seen daily by billions of people which is, well, an iconic part of your site's branding.
As for the rest, welcome to distributed systems. Any time you're working on something which involves multiple codebases on different schedules you're going to have a crossover period. For the web that period is measured in years since it has many clients and billions of users.
If you want to support higher resolution icons for Safari's pinned tabs or iOS/Android you can add those as well but that's an optimization for new way to interact with web apps which those device makers added and isn't necessary unless you expect lots of people to use that feature and your existing icon color scheme clashes with the system UI.
Purposeful != functional, and I don't argue that they serve no purpose. My point is it's a lot of detail work (i.e. BS) for something that does no 'work' -- it's a lot of overhead for a visual cue.
It's one line of HTML (/favicon.ico is the zero-code default) for a user-interface cue which is widely used. "a lot of detail work” is only true if your internal processes for adding a static resource are phenomenally inefficient.
If you are adding PWA support to your site and don't like the way your default icon displays on some devices, you have to add one more line of HTML and one small JSON file. That is more work but it's a fraction of a percent of the work which you will need to do to make a PWA for all but the most trivial sites.
The favicons are certainly functional - as a sufferer of 'too many tabs' syndrome, at the very moment, the only information I have about each of the ~30 tabs currently open in my Chrome browser is the favicon.
This packs far more information into the 48x48 (or whatever resolution) then trying to squeeze in a title like "Am" or "Ha" for Amazon or HN.
(Totally agree on the complexity, seems like it followed the iOS Store model of interface design!)
