Max's got a bit more explanation here: Creating a Flexible Tumult Hype Document within a DIV with no set 'height'
just to mention:
there are differences in how to achieve the responsiveness. and not every hypedoc will fit to one of the above solutions. it's highly depended to the document-setup ... and of course to the environment later on ..
though the proportional resizing regarding Hypes Layoutdimensions is robust and will work well either using scale or resize there may also be necessary adaptions regarding the event to fetch to apply the scale/resize. eg if a Hypedoc makes heavily use of scenetransitions it'll be better to bind the scale/resize to the resize-event of the window or observing the dimensions of a Parent-element of a hypedoc instead lean on Hypes LayoutRequest-Event