Hello, good day and thanks for your question. Just to check and confirm, what is the macOS that you have on your device and the version of Edge, is this not the behavior or the case from the previous version? Checked this on the latest macOS Tahoe with the latest version of Edge and since you will not be able to change the behavior of the shortcut directly in Edge, the next option is to go to System Settings > Keyboard > Keyboard shortcuts > Windows > Halves > from there you can change the Tile Top Half and Tile Half Bottom.