I never thought I’d see the day macOS would get tiling window management. Wonder how it will interact with Stage Manager if at all.
You still haven't seen that day, have you? macOS still offers only a floating window manager, now with some window snapping capabilities. But there is no mode or window manager built into macOS where new windows are arranged in tiles spanning the whole screen by default.
I really hope there is a "automatic tiling" option, otherwise this is just mouse support for the current "Move Window"/"Tile Window" options already available on the OS (and easily bindable via custom shortcuts).