Split off from #30671. See the second part of the original post, and this doc for more context, but in summary resizing, at least on macOS, causes extremely visually janky "jumping" of content relative to the upper-let corner, and on all platforms expanding flashes a color that may be very jarring (e.g., black in a mostly-white app) in the new regions.

Update by @iskakaushik on Sep 23, 2020:

I've made this issue an umbrella issue to cover desktop resize issues across all desktop platforms. This issue will be considered closed when all the sub-issues are fixed. My understanding is that the behavior in linux is good (not janky). This now tracks smooth resizing for macOS and windows (non-UWP).

Update by @knopp on May 3, 2021

This is actually a problem in Linux as well, reopening the issue until Linux resizing is fixed.

• Smooth resizing on windows (Win32) #66475
• Smooth resizing on macOS #66476
• Smooth resizing on Linux #81677