I think this has gotten heavily exaggerated by the community over the years. The way I remember it back in the day was less 'There's nothing inside this tellyporta it just works on magic" and more "Somehow and ork can fire this shoota for hours, but when a Tech Priest tries to fire it they have to clear jams every twenty or thirty rounds". Like the WAAAAGH field would nudge bitz just enough to keep them working, it'd keep circuits from frying, It'd nudge the Mechboyz to work a little harder on the Red ones. Magic, but not as overt as when people say Ork tech is just a bunch of junk cobbled together with no worky bitz inside. Iirc the old lore had the Old Ones encoding huge amounts of technical information in the Ork genetic material, such that when Mechboyz started thinking real hard about how to solve a problem they'd just know how the principles behind an engine or a force field or whatever, and be able to apply that programmed-in knowledge to kludge something together with the materials available to them. Feral Orks can go from the stone age to space travel in a few decades because all the knowledge needed to wage the war in heaven was built in to them when they were designed.