Even if the scroll arrangement itself doesn't go to fill parent, why doesn't another component set to fill parent that is in the scroll arrangement stretches it? I mean, it doesn't stretch its background. But it does work with pixels and percentages.
because it is a scrolling arrangement and therefore there is nothing to fill.....
we are getting into the realms of quantam physics and Schrodinger's cat now 
I appreciate the animosity about the topic.
@TIMAI2: I tried your aia, but that's not what I wanted. TIMAI2 puts a SVA inside a VA which contains other objects. That VA doesn't offer scrolling and squeezes its content to fit to the screen when I rotate the phone. What I want is a VA which keeps the original proportions (more or less...) and offers scrolling if due to the changed height of the display some objects fall outside the display.
The work-around that I'm using to fill the entire screen is to insert an empty label (well, not really empty, it contains a space) which is set to fill the parent, with the expectation that this stretches its container to fill the display. That's exactly what it does with the non-scrolling VA. Why can't a SVA behave exactly the same?
Some may say that an SVA has an unlimited height and therefore "stretching to the full size" is undefined, but the way I see it, it should just stretch to the size of its non-scrolling sibling on a (vertically oriented) display and then scroll if there is more content that what fits on the screen.
Just my 2 cents.
I didn't. All my arrangements were placed directly on the screen.
Which is what I used to fill the gap between the VSA and the VA at the bottom
Correct
Try all them not in property but in blocks
When screen 1.initialize
Set vertical scroll arrangement .height percent 100
Set vertical scroll arrangement .height
And so because I saw it behaves differently in blocks