It's either finger trouble over at the DVLA or a dealer demonstrator that got stuck in a corner after production ceased and forgotten about. There's always been late registered vehicles - M-plate Novas in the 90s when they finished on K-plate for example - they're just the detritus of systems that aren't as tidy as people think they should be. BMW would have no idea about it unless you gave them reg and VIN - and then they would only say that, yes, it was registered in 2019 but wouldn't have a clue why. Assuming it's not a phantom, the reality will be a lot less interesting that the mystery suggests.