My guess is that the details of implementation for both of the mousedown and mousemove events are slightly different between chrome and Firefox, and this ends up in radically different behaviours because of the "on the fly" instantiation of the event listener.
Solution:
Make it so that the clicks are consistently blocked.
Have the user initially on the Panel List tab, instead of Page Layout, because the Wizard is activated from the start and there's no explanation about it in the Page Layout UI. This way it's easier to figure out what's weird with the panels here.
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