I vaguely remember reading that when the S&W .460 was released, factory ammo had to be downloaded a little from SAAMI maximum. I think max was around 55,000 psi, but manufacturers found they got sticky extraction at that pressure, so backed off to around 50,000 psi.

Is this comparable at all to .38/.357? I don't know, but if the .460 doesn't show extraction problems until 50k+ psi, I certainly wouldn't expect a .38 to show any at 20k psi, or even a .357 at 35k psi.

Every reloading manual I have ever seen talks about hard extraction and flattened primers in their RIFLE sections, not the pistol sections. Most pistols don't reach any where near high enough pressure to show such signs.