If you mean the "Fit to screen" zooming feature it is there (bottom right corner).

But if you're talking not only about scaling but also about re-arranging the sketch elements based on the screen size (in a classing web-app manner), then yes, it doesn't work.

This is a bit challenging to do for the free-hand drawing of absolutely-positioned and scaled elements since the app might not have enough context of how to re-arrange. I.e. there is a free-form arrow that goes from the exact word of the sentence to the exact Attachment of the Mixer (it is not clear how to redraw it from horizontal to vertical form-factor).