When it comes to primary definitions, I throw out all of the considerations other than the physical laws of nature. Interpretations dealing with whether or not the meaning of a photograph was real, deceptive, incorrect, misleading or inaccurate are human-generated baggage borne of each individual viewer's past history and agenda.
For me, the defining characteristic is that the subject was rendered and preserved on the medium in situ (thanks, Maris) in real-time by the light reflected from that subject. And the medium, in order for that to happen, must have been in direct line-of-sight proximity to that subject at the instant the rendering was realized.
Thus the two are inexorably linked forever. The moment came and went, and will never repeat in exactly the same way. And the medium, having faithfully recorded that unique moment, can never be exactly duplicated because that now-past moment can never be originally repeated. And thus is born that first-generational state of provenance.
Now, 'blansky' once challenged me with the Weegee example. Weegee was well known for "rearranging the bodies" before his tabloid photos were exposed. Didn't this alter the reality of the scene on the resulting negative? No, I responded, because the resulting negatives were accurate first-generational renderings of those rearranged bodies. The deception, intended or not, was the photographer's, not the camera's.
To the extent that I trust the LOC, I too am comfortable accepting that linked scan as a representation of the glass plate it depicts. But I do so in recognition of the fact that I am also aware it does not—and cannot—absolutely prove that representation. The acceptance of the scan is a matter of convenience, not a matter of provenance.
I mean, if I were bidding to buy that plate I might up my bid based on what I saw in that scan. But I would never sign the final check until I had seen the physical plate in person and held it in my own hands.