nope, the viscosity of oil mixed into gas has nothing to do with anything. in the engine the gasoline readily evaporates and the oil condenses onto the working surfaces.
that klemm article is pretty good but i expect my pistons to look like that after 1000's of miles not hundreds. they are tuned on a razor edge. you can see that oil beginning to varnish on the skirt, once that builds up you're hosed. get enough varnish to stop heat transfer and you will have a four corner sieze in seconds.
these guys are running much hotter piston temps than you see on even a pretty highly tuned moped. plus you gotta remember piston velocity on a 60 mm stroke vs a 40 mm stroke is way way higher so 7000 rpm on an H1 is probably like 10 or 11k+ on a moped... too lazy to do that math, but that is some true ragged-edge shit. not to mention not a lot of fin capacity relative to the power output, always a limiting factor in vintage racing.