If you have described your item correctly and have backup in your listing

 good pictures, details, custom item specifics - then eBay will stand behind the seller even in cases of SNAD claims.  It all depends on what the buyer is claiming is SNAD and the item category.  Some categories, it will be tougher to prove that the buyer has filed a false SNAD.  I sell clothing, it's easier to defend yourself against a SNAD.  Someone selling electronics would have a harder time depending on the issue.  i.e., seller says it was working when packaged, buyer says it's dead on arrival.  In that case, it would be buyers word against sellers word. I don't know which way eBay would go.

But having a "No Returns" policy does not mean eBay assumes the seller does not want the item back.  And it also does not mean eBay will force the seller to refund no matter what.  True SNAD, yes, because that's federal law and eBay has to enforce it.