I'm afraid your interpretation is wrong.
Let me go through how repeater and responsive layouts works:
Responsive layout/mashup first:
It takes all space that is available to it and stretches itself (and responsive content) to fill up the whole given space. It has no height or width properties when it is not in some other container. ex. If you'll put timeserieschart widget in Responsive mashup and open it in 1920x1080 window, then it will fill 1920x1080 px. If you resize window to be 10x10px then it will be 10x10px. With fully responsive mashup, you should never see scrolling bars. So Responsive mashup/layout takes width and height properties of its parent which is window for mashup.
With "Static mashup" - in the moment when you are defining 'Mashup' property for Repeater height of mashup you just passed is calculate. You can see that FixedMashupHeight is filled with height of this mashup. If you set any smaller number, than it will be trimmed. But if you set 0 than it will be full height.
With "Responsive mashup" - as described above, responsive layout don't have height or width dimensions on its own. It takes it's parent dimensions. So if you define Fixed MashupHeight with 1px it will be 1px. If you set 0 then it will disappear at all, and resetting to 200px prevent this behaviour.
For Repeater contained mashups you should build 'static mashup' or calculate how much space your responsive mashup will need. There is no other way.