New iMac - is this a feature or just something wierd

My new M4 Mac arrived today. I am delighted with it, and it's now all set up and ready to start paying back my investment. I have noticed something unusual, and I don’t know if it is supposed to happen, but if it is, it's very useful.

The M4 will supplement rather than replace my existing M1 and now sits alongside her. Some of my work will benefit from having the ability to AirPlay from the M4 to an extended screen on the M1. However, there will also be times when I'd want to use the M1 as a second computer. Therefore, I decided to switch between AirPlay/extended screen and a two-computer setup as and when appropriate.

What I noticed, though, is that when Airplay is off, and I’m using them as separate computers, when I move the mouse on the new M4, the cursor will move off the edge and onto the old M1 just as it would if I were using AirPlay. Similarly, when my (M4) cursor is on my old M1, I can type with my M4 keyboard into whatever window I've selected on my M1 with my M4 mouse. I've also noticed that I can do this in reverse, i.e. use the mouse and keyboard from the M1 and use them to operate M4 when the mouse moves the cursor from the M1 onto the M4 screen.

Maybe this is a feature I’ve enabled without knowing, if so, it’s very useful for me on my own, but if I was working alongside someone, it might be a bit chaotic.

Thoughts, please.