With public toilets, the plate WOULD be used after someone finds the toilet, but if the toilet can’t be fixed “on the spot”, the installed plate would make people use the other cubicles. Cleaners in Australia have been installing them on broken toilets and then contacting plumbers to fix the problem.
The main purpose for the plates is to stop tradesmen using newly installed toilets on construction sites…forcing them to use the portable toilets that have been provided. There’s not much point having all these OH&S regulations for the supply and maintenance of portable toilets for tradesmen, when in rooms next door there are toilets full of faeces…