I have the same issue with my shiny displayport monitor when i turn it off, while the secondary, 180€ HDMI-monitor simply does not care at all. IIRC, it’s a combination of Nvidia GPU + Wayland + DP that triggers it on my system, my logs muttered something about the display not being unregistered, which causes it to not turn on because it cannot be created - details are hazy, i simply do not turn it off anymore