I don't think that's the case at all. As TonyJZX says, they're going out of their way to sell the "Britishness" of the car - look at those wanky tail lights! They're also made in Cowley in Oxford, which is pretty English as far as I can tell. It's never been pushed as part of the BMW brand because that, for a long time, was sold on its 'Ultimate Driving Machine', rear-wheel drive nature, and Minis have always been front-wheel-drive.
Minis are certainly marketed as being just as British as Bentley and Rolls Royce are, and as much as SEAT is Spanish, Skoda is Czech and as Lamborghini is Italian, regardless of whether we know they're all essentially German now.
ETA: They're even putting a light-up Union flag on the dashboard! Not very Germanic...
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