Stolen scan?

I checked and there are two Jordan Rookie PSA 10's currently on Ebay. Both have the same cert. number. What is the the deal? One of the sellers is PSAStock, who seems reputable enough. Although, why on earth wouldn't you have multiple single card scans when you are selling cards the caliber of a PSA 10 Jordan Rookie and a PSA 10 Lambert Rookie. PSAStock shows both of these gems in a 4 card grouping.
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I wonder whats up with this auction...
1996 Select Certified Mirror Gold Ozzie Smith
2006 Bowman Chrome Orange Refractor Chris Carpenter
If a buyer bites, they will buy the card from the owner and turn a quick profit.
If the sellers are ligit, it happens more often they we spot.
Nothing wrong with the practice as the owner of the card gets twice the
exposure and doubles the chance of the sale.
"I spent 50% of my money on alcohol, women, and gambling. The other half I wasted.
So if you are high bidder on one at 6500 with 45 minutes left and then another buyer clicks buy it now on the other one for 8000... you get an e-mail saying sorry card is sold....
Please explain why that is a good business practice.