Question on False Disk Ejection Messages

One possibility is that your external drive is trying to draw more power than is supported at the USB port.

To check, option-click  > System Information > Hardware > USB. Select your external drive as listed in the panel on the right.

Other things to check are the cable used to connect the drive. Change it for new or known good cable.

If your ext drive is running thru a hub, try connecting it directly to the computer.

Ideally if you're using a hub, that hub should be powered by an ac adapter instead of the computer.

Che Dog wrote:

Disk Not Ejected Properly notification is false.

Actually, those messages usually indicate that the disk hasn't been ejected properly.

That's not to say that you were the one responsible. From what I gather, there's a long history of external USB drives sometimes getting dismounted improperly when you put a Mac to Sleep. I'm not sure if it is the Mac, or specific enclosures, that are responsible for that.

If you connect a drive through a USB hub built into a monitor, and the monitor cuts power to its USB ports when putting itself to sleep, that could be another way to run into the issue.

How to stop from incessantly repeating?

You could try using "Lock Screen" (and possibly also turning an external monitor off), rather than "Sleep". Or even shutting the Mac down completely. My Apple Silicon Mac boots from its internal SSD very quickly – it doesn't take much longer to power up than older Intel-based Macs took to wake up from Sleep.

I've experienced that quite a bit with Sequoia and Tahoe on my M4 Pro Macbook Pro. I find if I wait to disconnect for about five seconds after the icon disappears from the FInder or desktop, I don't get the message. My external SSD (1 TB OWC Envoy bus-powered with usb-C cable included) is about half full.

It "feels" like the drive or the OS are still doing housework after the diver icon clears.