I had a well known knife dealer send me a SK5 version not knowing it was not O-1. They weren't aware that O-1 Cold Steel blades are marked as such, but they do have the same model number. That's what caused the confusion in my case.
If you can have the dealer check for the O-1 marking on the blade. Unmarked ones are SK 5.
I decided to keep the SK 5 model as the other one I had was the Chinese SK5 with the black coating. The Taiwan SK5 blades were built very well, excellent fit and finish and had been changed to a more accurate, well controlled Mar temper heat treat. I like O-1 and still may get one but the SK5 version was so nice I had to keep it.
I don't do business with Amazon for the reason you gave but they aren't the only ones that made mistakes with the rolling change using the same model/sku number. My dealer is even one of the dealers that do business here and I have used them for 10 years. They checked the knife but at that time didn't know about the O-1 marking on the blade.
To be honest, the performance shouldn't be that much different. They both are getting excellent, precise heat treats and the old design has been tweaked over the years to eliminate areas that could cause weak spots & stress risers. As long as it's real Cold Steel buy with confidence. Either steel is fine for me.