While velocity is important, concern over velocity difference is not something to lose any sleep over.
Ballistics by the inch, and everyone else's tests are interesting, and show general trends, but they are NOT an accurate predictor of what you will get with your guns and your ammo.
Your gun(s) and ammo might be very similar to the results they got. They MIGHT even be identical, but they also might be much different.
The ONLY way to know, for certain is to measure YOUR gun and YOUR ammo.
Everything else is just a guess.
I've seen 70-100fps difference in velocity between different gun with the same barrel length. I've seen a 4" turn in a few fps faster than an 8 inch.
Is this common? No. But it's not as rare as you might think.
Every gun and ammo combination is different, most fall close to the middle of the bell curve (naturally) and that's why the tests (and reloading data) are useful guidelines. But there is always the possibility that your gun & ammo might be at either end of the curve, where things are different.
Only testing what you have in your hands shows with certainty what it does, or doesn't do.
I've been loading and shooting .357s since the early 70s. S&W N frames, (4,6 & 8") Ruger DA and SA (6, 6.5") S&W K frames (4 & 6") and 6" & 10" Contenders and the 18" Marlin carbines. Also Desert Eagle and Coonan semi autos. I don't do .357 snub nose, No interest in them, for me .38 is enough in a snub nose,
The shorter barrel guns bounce more, and are louder (because the muzzle is closer to your ear). The bulk of a revolver is in the cylinder(frame) and grips. If you can "tuck" a 4" you can do a 6" about as well, usually.
Some people find the 4" points better for them, some find it depends on the specific model gun, more than the barrel length.