If a mini humbucker gives a more focused sound due to 'seeing' a shorter length of string compared to a standard humbucker, then a pickup which could 'see' 100% of the speaking length of string should just be a sludgey, booming mush shouldn't it? But who knows?
As Andy says, with all three of the Simms pickups on in MM mode you'll have a lot of the normal pickup area covered all a the same time.