The Peacekeeper is not on the same action as the Python, it is on the new Mk III/V action, the same as the Trooper, but is, as you say, a plain matte finish version without any extra internal work. It was intended to compete with the S&W Model 28 (Highway Patrolman) which was S&W's low cost version of its N frame .357 Magnum.
The idea behind both guns was to provide a low cost revolver in .357 Magnum, without the costly internal work and high polish of the more expensive guns. (Those of us here might appreciate the quality of a Python compared with a Trooper or a Peacekeeper, but try explaining to a cash-strapped city council why your department needs to spend a couple of hundred dollars more per gun for a shiny finish!)
No, it is not a Python, but it is a solid, accurate and reliable .357 Magnum revolver.