In addition, let's be clear about something. The creases that make an SGC 60 an SGC 50 do not show up in scans on ebay, where a huge amount of cards change hands. So, when you are purchasing 500 T206 cards on ebay over the course of a few years, and you want to be certain they don't have hidden wrinkles, you had better be buying SGC 60s. If you show me a PSA 4/SGC 50 that got bumped up/crossed over to an SGC 60, I will show you a card I am comfortable does not have any wrinkles in it and may now consider purchasing for more money than the PSA 4/SGC 50 was going to cost me, when I wasn't interested in it.
Same card, true, but some different assumptions now go into it with the higher SGC grade.
Here's a perfectly good example. I own this card. If I saw this on ebay, the only way I would know there is a wrinkle in it would be if the dealer told me in the listing (fat chance) or I understood how SGC graded its 50s. This card would be a 60 if it weren't for the "unscannable" wrinkle. If you popped this out and resubmitted it, the only way it gets to be an SGC 60 would be if this wrinkle didn't exist. In other words, the SGC 50 would have been an undergrade and the SGC 60 would be the appropriate grade -- and there would be a higher demand for it as a result.
I bought the Moeller below "in the raw" on ebay in 2000. The seller's listing promised the card had no creases, but it did. The next buyer of this card will now be full aware of its hidden defect -- a spider wrinkle on the left border -- because I had it graded by SGC and they gave it a 50 and not a 60.