SCART control, as far as I know, does two things - relating to pins 8 and 16.
It uses pin 8 for widescreen signalling (to tell the tv whether it's 4:3 or 16:9), and it uses it to tell the tv 'I'm here'. This usually means turning it on switches your TV to AV mode - this isn't the case with a B&O tv. But the widescreen signalling is useful.
Pin 16 signals to the TV to let it know that RGB is in use or not. With SCART control off, the TV will only take the PAL signal.
So - leave it on. And also set the output to RGB, as it's nearly always far better.