Joey,
it is inaccurate at best.
The roar at the start-up is a common thing to happen, not only for rovers. The viscous clutch of the engine-driven fan is farly stiff when cold, and it "loosens up" after a few minuts of engine operation.
How does one determine if the viscous fan clutch is bad? My '89 RRC fan clutch was pretty tight when it was hot, but that clutch was close to seizing and seized soon. My [other 4x4] fan clutch feels very light, but it does lock up quickly as the temperature increases. On that particular clutch, the temperature range between light and tight is about 5F - and it can cool down by 5F by the time you stop the engine, get out of the vehicle, and reach for the fan.
In contrast, my yet another 4x4 has a heavy-duty clutch that always feels tight. And it never gets hot, so I was never able to feel what it is like when it is locked!
By the way, if a fan clutch allows the fan to spin an entire turn under any condition, it is definitely loose.