Thanks, @AHHans!
I was mostly curious if this was on purpose or a glitch. I mean: yeah, in real life, the lateral forces I was putting on this extended piston when landing on it would have definitely "moved" something. The piston still functioning while punched through the cylinder wall made the think bug, but there are a number of AXISGROUPS override properties for my bent piston in the save file that aren't there for the other pistons. So this is something the game is accounting for, however cosmetically awkward. Interesting!
And now I'm wondering what other parts that can be "inadvertantly modified" but still function. This is the first time I can recall seeing that.
MF