[soneil]

I didn't finish the video (yet, no fault of the video, just bad timing), but I don't think it's EMI - the "pre-current" looked fairly flat, and EM doesn't like flat. I'd expect EMI to show as a spike timed to match the leading edge of the signal.

[foxfluff]

I think the takeaway is that EMI looks flat for a while if you run half a kilometer of wire next to a half-a-kilometer long source of EMI.

The leading edge isn't there for one nanosecond and then gone, it travels down and continues to induce a current to the adjacent conductor, a current which must continues to flow.