I am glad you're going through an official ebay claim for an item not as described. Stay on top of it.

Yes, it is a bit suspicious the seller asked you to return and they would reimburse you later, if the cost of return is more than the cost of the item.

I suspect they were trying to disencourage you.

Stick with the ebay claim.  If ebay asks you to post it back, try to get onto a real live ebay rep (it takes time but can be done) to explain as you may be able to get a refund without returning it. I am not sure. I am a buyer & haven't had to go through this process.

But I have heard some sellers will elect to just refund and forfeit the item rather than arrange and pay return postage.