yes it is the case. you still have to set the global multiplier to the right place for the open loop conditions.

MSD software or original ford software, it's the same principle. the closed loop does not operate all of the time so the fuelling has to be right across the whole operating conditions contained within the map. the 'CO adjustment screw' multiplies all values in the map, so having it to far one way will mean not enough fuel at that point, and too far the other way will mean too much.

if closed loop is in operation, to some extent it doesn't matter what is in the map at that point (although the controller only has a certain authority, so cannot correct very far away from the base value) as it gets altered based on the feedback from the lambda sensor so can add more fuel or take fuel away as necessary.

so if you don't set the CO adjuster correctly for the base map as given in the instructions but twiddle it all the way one way to try and overcome a problem elsewhere, it may look like you have cured the problem at idle where the closed loop controller has run out of authority but it will cause you problems everywhere else.