Even apart from the monitor just hanging in the sleep state... a lot of them have glitchy behavior until you hard reboot the monitor. Some monitors actually will (internally) execute a full reboot of the monitor controller board when you wake them as a result, because they can't reliably come back out of the Deep Sleep state, and that's another source of the "monitor disconnects and windows moves my icons/windows" glitches. The monitor is actually electrically unplugging itself and replugging when it wakes.
Vendors don't really care because everyone (who's in the know) turns the feature off because it's broken and causes problems.
This particular EU regulatory exercise was a failure. Or at least, EU needs to rip off the bandaid and require that it be enabled with no option to disable it, which would obviously lead to problems and poor reviews, which would eventually lead to a fix... after a couple years of glitchy monitors.