Not weird really. Focus's et al are two a penny, littering every street in the land, so plenty of people need parts for them and that's one major theft category covered. Also, due to their prevalence, their locking and security mechanisms and systems are easily researched, making them a simple target. Also due to their prevalence, they blend in, so a passing Plod will hardly turn a blind eye as yet another Focus passes him by, no matter who's driving. Finally, as there are so many, owned by your average bod in the street, they get crashed.
Now, consider the Noble. Owners tend to be affluent and so won't be hitting eBay or a back street scrappers for parts. The security will be a new territory for any chancing scrote, and will probably be very good and multi layered, increasing the chance of either capture, or failure to acquire it in the first place. A Noble with a couple of track-suit wearing baseball cap'd numpties would be a definite alarm bell to any Plod, so they would get spotted very quickly. Finally, as the owners are probably wealthy car enthusiasts who've owned many high performance vehicles and know how to handle them well, they are less likely to have an accident. They may also be a recreational car, so driving very few miles, possibly only on nice, clear, sunny days to place where the roads are quiet, again minimising risk.
As a comparison, my mate went from a 330bhp £25k Subaru Impreza paying £900 a year to a 330bhp (that's nearly 700bhp/ton P/W

) £41k Ariel Atom and his premiums dropped to £470.