Ahh, that makes sense!
That gasket on my MP is pre-cut to allow for the little conduit that holds the wires from the group switch. Irritatingly, It's just kind of draped over the gooseneck, which means it often comes off when I wipe down the front panel.

One of my few complaints about the machine otherwise!

I edited my post to clarify that the instructions apply only to the GS/3 AV.