99% of the time it just won’t work, it’ll stall on preparing to sleep, etc. (which is why it isn’t supported)
Sleep mode is not actually putting the server process to sleep. It completely stops the server and waits for connections before starting the server again.
I do agree it would be nice for low-usercount modded servers since they take up a chunk of resources, but it’s just not viable at the moment.
However there are discord bots that can start/stop AMP servers:
https://discourse.cubecoders.com/t/3rd-party-amp-plugins-and-bots-list/2231