Mmmm OK I see why you'd get confused I wasn't very clear.
My normal minimum is 2000 RPM. With SMCFC running, the minimum I can set is 4651, which isn't the actual minimum, even when not on charge and idling with just Finder running (i.e. shouldn't be hot).
I'm wondering if there is a fix for this, so I don't have to shut down the computer and restart to disable smcfc. Thanks