It all makes sense when you fly a Category C machine in a cct in VFR/IFR situations.
When in VFR a 1500' cct is perfect. And you are following the local VFR rules..ie left or right hand ccts. In total, cct times are similar for all categories as a result.
In a circling approach (following an IFR instrument approach)(in a cct) max speed is 180kts and then you know that you are the only one doing the cct, so therefore do either left or right hand cct, whatever suits-you-sir. You just need to maintain obstacle clearance (400' for cat C) till on approach path/angle for the runway which could be as early as on an oblique downwind. These ccts are usually done at about 1000' and are limit by visibility.
Sorry to be so tech but it all works nicely.
