With the current system, I could easily believe that not all bars scan the barcode for a nefarious reason, but do it just to make it easier to avoid a bad manual reading (different ID layouts per state, darkness making it hard to read, etc.).

With this kind of digital ID, requesting anything more than my age and photo is an immediate flag to me that they're explicitly looking to do something shady (or at least they're incompetent and don't know how to use the reader properly). I would deny everything but the age and photo request, and if they balk, I'd ask to speak to a manager or just walk away.