The rendered height of a region does not change from its initial state after resizing. The rendered width does not change either, but line box width does appear to change, just not the rendered width of the line box. The attached test file has a region with 10% width and 10% height. If you open the attached test file and resize the window height, the number of line boxes rendered does not change. If you resize the window width larger, the line breaks in the text do change, but the displayed width does not.
Created attachment 103871 [details]
This has mostly been fixed. Opened new bug with remaining issue