Just because a designer had a particular projectile weight in mind does not have any bearing on that projectile being the best for the cartridge in question.

In 1935 when the 357 Magnum came out, the ammunition was built around a 158 grain projectile similar to the 38 Special offering of it's time.

in the eighty-five years that have passed since the 357 Magnum's Public debut, metallurgy has improved, ballistic knowledge was gained and new manufacturing techniques came on the scene

In that time we also learned how to put jackets around lead and a new world of projectile performance opened up.

The cartridge with the most 1 shot stops in the history of gun fights is the Remington 125 grain SJHP 357 Magnum. That will someday be exceeded by the 9MM just because of the sheer amount of 9MMs being used these days by Law Enforcement and the Military. Not to mention Today's almost total lack of 357 Magnums in the Law Enforcement world.

In this case a lighter weight projectile than the designer originally envisioned is being used

I carry 125 or 140 grain JHPs in my defensive 357 Magnum sidearms but load up the 180 grain Remingtons into the lever gun if there is Deer nearby

Almost never do I shoot 158 grain 357 Magnum ammunition

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"Acta non verba"