So many issues here ...
First, I think it is possible to give an opinion based on a scan because every such opinion has an implicit qualifier/asterisk that says "I am only looking at the scan. I don't have the card in hand. If I did, my opinion may be different." To the extent that everyone understands that the opinion is about the card as scanned and not as held in hand, then it is ok to me to give opinions (can you tell I'm about to give an opinion?
). We do it all the time in auctions and ebay and everywhere that we see a scan. Even if it's not something we post, we make the mental calculation as we try to decide to buy or not to buy.
In my opinion, this card AS IT APPEARS IN THE SCAN, looks like a classic example of trimming. It is not a diamond cut by any definition of diamond cut that I know of. The top border is clearly not parallel to the bottom border and has a slant that is dumbfounding in it's starkness. If we were assembling a tutorial on spotting altered cards, this one would be Exhibit A in the examples for spotting trimming. Edges that are slanted or not parallel are the Numero Uno sign of trimming, and this one has it in spades.
In fact, this one is so bad that it occurs to me that maybe it could not possibly have escaped the grader - he (or she) MUST have noticed it. Maybe then they looked for other signs of trimming like how the edges break, bats ears, different discoloration to the edges, etc, and didn't find any. If they didn't find physical evidence of trimming, they may have (reluctantly) concluded it was not trimmed despite the really bad slanted top. This gets us full circle in saying that maybe someone with the card in hand can see evidence that does not appear in the scan.
But even if that were the case, I wish someone (TPG, Goodwin, someone) would at least acknowledge what can plainly be seen instead of pretending it must be perfect because it has an 8.
As an aside, I agree with the others that T206 resource should not be called upon to ring in on this any more than anyone else. They have put themselves out as experts in the T206 set in particular, not in general alteration techniques that apply across all card types. I think they are perfectly correct to decline to comment.
But I don't mind giving an opinion on the scan only - that thing looks really, really trimmed!
J