Well, I'll throw in my measly thoughts here.
If you reload,, and use .357 brass in a .357, and download it to .38 spl levels,, especially light target loads,, there is the potential for a pressure spike problem.
A small charge of powder,, in a revolver,, will lay the length of the case,, up to the base of the bullet. The primer will burn across the top of the powder,, instead of against the powder, With SOME powder/primer/bullet combinations,, the potential exists for a pressure spike.
In the dark ages of my handloading beginnings,, I used a fair amount of .38 Spl cases,, with a light target load, (Bullseye powder,) under a 148 grn WC bullet. An oldtimer,, who shot bullseye competition,, taught me to add a "filler" between the powder & the base of the bullet to get a safer & more consistent burn rate.
But using .38 spl ammo in a .357 chamber, or even a .44 Spl case in a .44 Mag,, can often cause the dreaded crud ring. Since I hate the amount of cleaning necessary to be able to easily shoot .357's or .44 Mags,, in those guns,, I load a normal charge in each caliber. I use my .38's in a .38 cal revolver, and 44 spls in a .44 spl gun.
But knowing I can USE other calibers in a Magnum,, if necessary,, I can appreciate the option. But generally, I don't reload very light loads in a magnum case to help prevent the potential pressure spike that might happen.