My car was sat at the dealer from May until July when I arrived in the UK to accept delivery of the car.I suppose the issue here is that that wheel should not have been allowed to "escape" the wheel manufacturer's production plant, also if SEAT goods incoming QC were doing their job they would have rejected it.
So, option (!) having that single drag of black paint getting trapped under the lacquer is okay by SEAT and so I'd not expect them to replace it and so a local dealer would just "do something" else with it if agreeing to replace.
(2) having that visual defect renders it not fit for sale, and SEAT will cover replacement.
(3) SEAT needed these wheels to maximise output of these cars so they were willing to take a chance to authorise the local dealers to sort that out after the sale.
I'd be a bit annoyed if any of my cars ended up being handed over with any visual defects, just shows that that dealer is being slack/sloppy and has been caught out. Having said that, if my dealer was just going to try to "better/improve" any small paint defect, I'd be getting alarmed enough to just settle for a cash adjustment if that could be forced out of them - as it is only you that is being expected to put up with this small defect.
They definitely don't have an excuse for missing it.