When I use this in the latest version of GameMaker these days - 2024.2.0.132 - there's a second when the game first appears properly that the loading screen splash art takes up the whole size of the game before snapping to the standard positions you set up for the thing.
I avoided this when exporting a recent game of mine by using a slightly earlier release of GameMaker, but going forward, doooo you have any idea why this would happen? This is a bit of an older extension of yours so prob not the highest priority I understand~ but I certainly don't know how to fix this quirk..