The only thing that's missing is a mapping from 'symbol #28' into 'ascii #63'. Internally it's storing instances of symbols plus font data for those symbols.
Also, something to think about: an EBCDIC document accidentally printed as ASCII/8859-1 would have equally zero semantic meaning when fed into an OCR program. But I don't think anyone would argue it wasn't OCR.
A font doesn't need to be anything more than a series of bitmaps. And then each character location on the image, ignoring errors, references one of these bitmaps. That's how documents with embedded bitmap fonts generally work.
That mapping isn't a very big thing. Sometimes text-based PDFs don't even have it, and you don't notice unless you try to copy out and get the wrong letters.
