"and that a young woman who stays overnight in the home of a male friend would be found guilty by a judicial committee even in the absence of other elements indicating an improper relationship - again, that is well documented and an example in the elder's manual."
Not trying to be difficult, but Shepherd (2019, 2010) presents several cases of where that would be permissible as long as they don't sleep in the same room or bed. One that comes to mind is if the Brother tried to catch a train, missed the last one, and had nowhere else to go.
I agree with you that in practice that may not be enough to shield them from accusations of porneia or from stern talkings to.