Oh, I updated and that seemed to deal with it. Woo. Thanks
My take on the general problem is that stuff like not scrolling in response to input is a property of the layout rather than the canvas/generated openfl stuff, and should be embedded either directly in the generated html file, or included as a separate js file to the main one haxe generates.
That way if people use their own layouts it won't automatically not scroll, but if they look at the generated one they can see pretty easily how to go about disabling scrolling.