Yes it is correct,,,
.38 Special and .357 Magnum have the same diameter for the case and bullet,,,
The only difference is the overall length of the entire cartridge,,,
And power of course.
In other words, if you buy a .357 Magnum pistol,,,
you may shoot either .38 special or .357 magnum in it.
If you buy a .38 Special pistol,,,
you may only shoot .38 Special in it,,,
The longer .357 Magnum cartridges will not fit into the cylinder.
Many people shoot .38 in their .357 magnum revolvers for two reasons,,,
The ammunition is cheaper for practicing at the range,,,
The recoil is much less and is more comfortable.
I hope this helps,,,