I think he has the two areas mixed up, the buyer, not KING2011. King, I hope this information I found in the Wiki about hone wear will help the buyer understand about hone wear on the spine.
"There are various reasons why divergent angles may be present at the bevel. Some are fully intended, for instance when a razor was previously honed with a layer of tape attached to the spine. This is a perfectly sound method to prevent hone wear at the spine of a razor."
Here is where I found it:
Bevel-setting in theory and practice - Straight Razor Place Wiki
Also, here is the SRP Wiki info on the parts of the razor to help as well:
The straight razor - Straight Razor Place Wiki
I hope Sir this information will help you resolve the issue with the buyer. IMHO, I think the buyer has the parts of the razor confused.
I wish you the best in resolving this.
Patrick