Regarding the Model 67 and the .357-rated load that you sent through it...

It has long been my THEORY (only a theory, no empirical data, zero evidence, no inside information and I didn't stay at a Holiday Inn Express last night) that modern K-frame .38 Special cylinders are no different than modern K-frame .357 Magnum cylinders except that they are slightly shorter and with shorter chambers.

Why?
Typical industrial manufacturing, process, stock and COSTS.

Production on a large scale... it makes far more sense for Smith & Wesson to basically have one part (a K-frame .357 cylinder) produced exactly the same way and then adapted for it's specific destination. In this case, there would obviously be two parts (carbon steel and stainless) but for Smith & Wesson to produce and stock a load of cylinders that are only appropriate and spec'd for the 18,500 PSI Max pressure of .38 Special+P all the while producing and stocking .357 Mag K-frame cylinders meant specifically for 35,000 PSI would not make sense in large scale production and it would likely cost them more money.

I'm not suggesting that we all take our Model 10's and build red-hot bombs for them, but my theory says that any Model 10, 14, 15, 64 or 67 is quite likely to be oblivious if you put ten boxes of ".357 loads stuffed in to .38 length brass" through them.

I believe the modern Model 24/624 .44 Special is built the same way, easily handling loads far beyond the anemic limit of .44 Special.