Does the "photo of a black hole" taken by EHT actually depict a visible light-based scenario?
You are right that the image is not a visible light image. It was taken using very, very short wavelength microwaves -- the wavelength is 1.3 mm which is only a bit shorter than the Far IR!

I think you may be reading a bit too much into the word "photo" which, as you say, has the everyday meaning of "taken with a camera using lenses in visible light."  I think most astronomers would use the term "image" rather than "photo" -- if you look at the NSF's press release, for example, you'll see that it uses the term "image".  (Links to all six of the papers the EHT team has published are in the NSF press release if you want further details.)

(I'd bet that "image" was changed to "photo" somewhere in the journalistic process as being "more meaningful" to the average reader.)

The appearance to the naked eye would probably not be terribly different, since the photon orbits don't depends on frequency.

As far as whether it got "boosted" or not, you're right to be very skeptical -- university publicity offices are prone to exaggerate and sometimes pump relatively ordinary science into amazingly important-sounding "breakthroughs."  In this case it all seems pretty straightforward, though. And there's nothing special about a visible-light image over a microwave image -- both are useful and neither tell us everything. (It is not uncommon for images in the visible to be among the least useful -- with X-ray or radio actually telling us much more.)