While I agree with most of what canada-banknotes has said, this particular example actually seems fairly accurately graded and consistant with what I would expect (both the before and after).
As coinsplus indicated, the note was "repaired" if you can call it that. If it had gone from 58PPQ to 66PPQ then I would have an issue with it, but 63 (without the PPQ) has always been synonymous with "pressed AU" and the note is exactly that. In any case, 63 is almost always a worse grade than 58 PPQ or EPQ.
Also, this is a 10M note which is expected to have flaws. The 10M collector knows and accepts this and isn't really going to get bothered over a 58 vs 63. The main issue was that the note was overpriced, not that it was overgraded. In fact, I would happily buy it if it was priced a little more realistically, whether it was in a BCS 50 or an LCG 58 PPQ or a PCGSBN 63.
I don't think any of the US grading companies make any pretense of following the Charlton's grading standards. Looking at PMG's grading standards (
https://www.pmgnotes.com/paper-money-grading/grading-scale/) and comparing them to the Charlton Catalogues, I would suggest the following equivalence:
68-70 = GEM
66-67 = CHOICE
64-65 = UNC
58-63 = AU
50-55 = EF
I do sometimes see 66PPQ and 67PPQ with obviously pressed center-folds which is certainly something to complain about but that's not what we see here. I've seen these more egregious cases mostly in LCG or old PCGS holders.
On the other hand, I find that PMG has been pretty consistent lately (provided you follow their published grading scale), even more-so, dare-I-say, than BCS.
At the end of the day, buy the note and not the holder. Value is subjective. Pay whatever you feel it is worth to you, regardless of what the holder says or what the Charlton says.