Summary
When the Epic Games Launcher has the “Minimize to System Tray” setting enabled, the app doesn’t remember its maximized state when it’s closed. This means that when I maximize the launcher and close it, it doesn’t remember being maximized and opens as a minimized (smaller) window. Disabling this setting allows the launcher to open normally. However, I want to use this setting without having to deal with a minimized (smaller) window each time I open the launcher.
If that setting is on, then the launcher is closed while maximized, and then the background tasks related to the launcher are manually closed in Task Manager. When the launcher is reopened, it remembers being maximized. However, closing and reopening the launcher normally will cause it to reopen as a minimized (smaller) window.
So, when the launcher opens from being minimized to the system tray (running in background), it causes the app to forget what size it was when it was last closed, and opens as a minimized (smaller) window.