Well, this plate doesn't choose which output is the correct one. Something else has to look and decide which number-correspondent-band is the maximal/correct one. But I don't want to argue that specific distinction. If you want to call the waveguide a recognizer, I'm ok with you doing that.
The whole presentation of this article is very "woo". They say bullshit like "the glass learned to bend the light". This is clearly stupid and false. The system DESIGNING the glass learned how to construct the glass such that the light bended appropriately. The glass hasn't learned shit.
Picking which of the 10 bands is the brightest has got to be trivial, so much more so than directly recognising eg. '4', so it does seem to do what it says.
> The system DESIGNING the glass learned how to construct the glass such that the light bended appropriately
With a bit of rephrasing you could say exactly the same about a neural network surely. The learning was embodied in the glass, so depending on definitions, the glass was 'taught' something. It 'learnt' something.
I kind of see what you're saying, but it does seem to be discounting something actually interesting and new (in my experience).
I don't see how your first and second statements are mutually exclusive.