Since I've only done the MFS once in July and 7-8 times in September, my guess is that my comment was about the Main Salmon in July and August. That's the time of year I do the Main Salmon. III-III+ is about right for the MS in summer.
MFS is always a III+-IV in my opinion. Lower water takes a lot of attention to not get stuck. Like late season Deso, only turned up a notch.