There is a blanket “suspension parts must not allow movement other than normal travel” (one which Penske has been nailed on before) but they probably want to use the more specific rule when they can. I also think they didn’t find the actual part that allows the shift or the flex.

Yes, it’s rear steer, or “skew” in NASCAR lingo. Penske did something to let the rear end shift relative to the trailing arm and probably the symptom is that the spacer block between the two gets rocked up on a corner where it’s supposed to sit flat. There’s a cheated up part (maybe the panhard bar can get longer?)…

Sometimes I wonder if Jack owns a factory that makes miniature models of factories.

In fact, this work is done by Jack Roush’s company Roush Industries, up in Michigan, which does contract engineering work for a number of industries. They also make the Google car.