There is a better way!
Why, all of a sudden, are we worried what eBay does? They just want the extra $0.15 for the second image. I will only use the obverse of my graded coins for sale. It has all the information, as well as the serial #. If eBay doesn't like it, I'll put it on eBid for free. If you are worried about a particular NGC or PCGS slab's authenticity, there is a place in both grading services to check any slab they have graded. NGC's is on the pulldown of grading and submissions. If you still have any doubts, they both also have excellent CSRs that can either validate, or direct you to someone that can.
I am more worried about counterfeit, or "doctored" coins getting graded. Private mints are doing wonderful work with all the new technology. Buying raw coins, at premium prices, and finding them to be misrepresented, is devastating. It is bad enough to have a genuine coin that cannot be graded. Believe me, I know.
With the guarantee of what's in the slab, I know that both grading companies are subject to human error, and subsequent coin authenticity issues. They are covered by insurance for this. With the problems I've had with grading issues, I am still relatively secure in trusting the major two grading companies with my coins. I also precheck all graded slabs I intend to purchase.
When you buy a slab, check the number. If eBay should do anything, it would be to stop "generic" imaging. The "WYSIWYG" method has always worked in the past for everyone. The other thing is to establish trusted dealers and as always, caveat emptor.
That's my story.........and I'm stickin' to it.