Running Windows 10 v.1903 and Illustrator v.24.0.2; with Illustrator open and maximized in the background, when double-clicking an .ai file in explorer, or right-clicking and selecting "Open with > Illustrator 2020", the Illustrator window is resized (usually to it's smallest possible size).
Running Windows 10 v.1903 and Illustrator v.24.0.2; with Illustrator open and maximized in the background, when double-clicking an .ai file in explorer, or right-clicking and selecting "Open with > Illustrator 2020", the Illustrator window is resized (usually to it's smallest possible size).