Regarding pulling off backs and heads for a look see, I guess I was brought up in a different generation. You see, I have no problems with doing it, because somewhere in the life of the engine, I'm going to have to do it anyway. I've done it enough times to be comfortable with it. And, regarding whether there's swarf or not, normally you'd expect that not to happen even in our so called modern engines, but it does happen.
So, to each his own. But digressing a little, sometimes you come up with some interesting things in buying used engines, or even so called NOS "new" engines. And, I've have a few stories with even brand new engines. We live in an imperfect world.
I pulled off the head of a then new Thunder Tiger .07 Schneurle, found it missing the head gasket. I contacted the company and they promptly sent me out a new head gasket.
Yet some folk are better off not touching stuff. I just repaired a 5 YO lawnmower that the previous person didn't know how to maintain, did his own disassembly and tried to fix it on his own not knowing what he was doing, messed up the governor, automatic choke and muffler system. It was a problem with the fuel line, swollen and closed off from ethanol, carb was badly corroded by ethanol inside, easier and cheaper to replace, under $50 in parts restored it to factory running condition.
To such I'd say leave engines alone.