The bug
When you disable the GUI (using F1) and then reload resource packs (via F3+T), the loading screen will not be displayed correctly. It looks like it always assumes a virtual to real pixel ratio of 1:1.
MC-144588
The loading screen for reloading resource packs doesn't cover the whole screen if the GUI is hidden
Resolved
Fixed
4
(Unassigned)
Confirmed
UI
Minecraft 19w08a, Minecraft 19w11b, Minecraft 19w12b, Minecraft 19w13b, Minecraft 19w14a, ..., Minecraft 1.14, 1.14.4, 19w34a, 19w35a, 19w36a
19w39a
Retrieved
The load bar for reloading the resource pack is a fine addition for information on how long the pack takes to load.
However while developing my resource pack it's getting to be quite annoying seeing a bright white screen with your company logo every-time my pack is reloaded during testing.