A gauge without #s is a hair above an idiot light, but really only has 3 steps. Cold, Warm, Oh crud, its going to overheat (as when your car does overheat, the steam spewing out the radiator should be obvious enough). Not surprising that many cars actually have center weighted gauges as well, so that as long as the car is 'warm' it will always be in the center regardless if its warm in Phoenix in July, or in International Falls in Feburary.
Anyway, with that logic, Its not surprising at all the MINI gauge would be designed to stick straight up during normal driving, since the non chrono one sticks exactly horizontal. As harold has said, people like gauges that point in a fixed direction, and manufacturers like to not have people bring their cars in for problems that don't exist..
You should be able to watch the oil pressure go from an idle state, to if you stomp on the gas and run the car to redline, its maximum pressure. (But wait till you're out of breakin to do that

) Barring something rather uncommon and a channel getting plugged or something else weird, oil pressure is 'broken' when its very low, indicating there's probably a leak in the system and oil is going where it shouldn't go. So if it stops rising and falling with engine RPMs, you also have a problem, because you're probably pumping it to a bad area instead of pressurizing it.