Now here‘s my half-remembered version of the actual story; this late at night I might get something wrong, but it‘s too difficult right now to dig out Bob Best‘s book, which is the bible on these:

The .38 Special is longer but the same diameter as the .38 Long Colt because S&W was hoping to sell the military on the new .38 hand ejector and this way both cartridges could be fired from the same gun, making the S&W attractive both to civilian and LEO shooters who wanted the hotter Special and the US military who wanted to use the Long Colt.

The DA Colts were bored through until at least 1903, meaning .38 Special will chamber without a problem. In fact, once S&W started writing “.38 S&W SPECIAL & US SERVICE CTG” on the barrels, Colt began advertising that their DA revolvers too could shoot both cartridges; this was not accompanied by any engineering changes like reinforcements, but large-scale blow-up disasters are not reported in the historical record.

At least some models, like the Officers Model, were supposedly actually shouldered for the Special, and from 1903 a slightly smaller barrel diameter was adopted for better accuracy with .38 Special. I do not recall the exact circumstances.

Obviously, don’t even think about any .357 Magnum loads.

No, they can’t. To anyone familiar with old Colts, the PP and PPS look so different from this DA Colt that it is immediately obvious, the way you could probably tell a Model 36 from a Model 15 right away.