Loading window appears to one side before it is resized upon launch

The Bug

As the title of this report suggests, the game's loading screen window, before displaying the 'Mojang' logo, displays to the side for a moment instead of it being centered (as in prior versions before this loading screen changed). Is this intentional?

How to reproduce

• Launch the game
• Issue is visible just before the 'Mojang' logo window is displayed (this would not happen in prior versions to 1.13).