The standard 38 special round operates at a pressure of 17,000 psi so those guns are built to handle that pressure. There is a technical standard called SAMMI that sets this pressure .
A 38 special +P is the same size round just more powerful. It normally operates at or just over 20,000 psi, because there is no industrial standard that defines the pressure of a +P 38 special.
A +P 38 special gun must me built stronger to handle the increased pressure, often these guns are built to handle about 22-23,000psi to insure they can handle whatever pressure the round is .
You can fire the low pressure 38 special round in a +P gun, it's plenty strong enough. But fire a the high pressure 38 special +P round in a standard 38 special gun, you may get lucky and your gun will just break or wear out quickly....If you're unlucky, it will EXPLODE in your hands. Taurus clearly labels the M85 38special ammo only, because I believe they want to reduce their liability. There website is there to sell firearms and is not always up to date. What does the instruction manual say?