I think you've generalized way too much and have come to some incorrect conclusions.Big engines perform better with a narrow LSA (if max power is the goal).
A narrow LSA moves torque downward in RPM and increases maximum torque but narrows the torque band.
A wide LSA moves torque upward, decreases torque, and widens the band.
Big engines are less sensitive to LSA, and certainly don't necessarily need small LSAs.
A small LSA doesn't move the torque curve downward. It does make it narrower. The rpm where the best torque is made is dependent on duration.
A wide LSA doesn't move the torque curve upward. It does make it wider.
A wide LSA does make idle tuning easier. That's why an LS7 can idle at 500 rpm and make good power up to 6000 rpm.
Vizard explains that the ideal LSA for a given combination is dependent on intake flow/intake valve size relative to engine size. If the intake size/flow is compromised for whatever reason, then narrow LSA is probably in order. RPM is a factor here too. I.e., how big does the intake valve need to be for a given engine size/rpm limit?