Sounds like they are trying to cover themselves both ways. Rightly or wrongly.
Firstly by only giving a warranty if they fit it (which they cannot do) I assume so it's fitted correctly to prevent any warranty claim for a fault caused by incorrect fitting. Unlikely
Secondly by putting it as scrap so you cannot go back saying its not "fit for purpose"
I think the point nos is trying to make is that the warranty may require them to service it in order to "qualify" (which shouldn't be the case)aim which case you'd have to return it to them in the event of a claim/service being needed within warranty. If your not able to do that then it won't matter what warranty they are offering.
I'm sure there is a compromise somewhere to secure a sale.
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