I use a single 34" 4K monitor with an arm mount on my Mac Mini. The power button on this monitor is one of those touch sensitive ones on the bottom right that I sometimes accidentally brush past. When I switch it back on, every single window gets reduced into an incoherent size and everything gets moved to the top left. It's really annoying.

I'm thinking of flipping my monitor upside down so I'll never accidentally brush that area while picking up something on the table.

That's likely a firmware bug in the monitor. It probably reports some ridiculously small resolution during its boot process and macOS queries it that time and rearranges the windows accordingly. macOS could implement workarounds of course, but probably it just follows the process whatever the display id protocol prescribes...