I think you have answered everyones question with your final line...

I quote

I also did that, and nothing collapsed, not even my expectations (which, admittedly, were zero).

says it all ....and shows this was not an impartial or valid assessment....imo

Why can't you accept that other people might just be able to hear things that you can't......

I'm happy that you can hear these things for whatever reason .....

Why can't you offer me the same courtesy ?

I've never told you that what I'm hearing is correct [though I do know I am hearing it ].... it's  backed up by all the other people I've mentioned and their posts, that you have ignored.

I can't second guess the conversation you had with the dealer ....maybe he's not up to much ?  There are similar dealers in this country too ....who for what ever reason don't pass on all the information available ......

I also note that no mention was made of listening in the dealership .....thats down right odd.  I've only ever been offered a home loan following a dealer demo.....this case in point.

Did you forget to mention the the reactivation process too ?

If the unit doesn't work when you get it home ....there are some specific things you need to do ...I assume you followed these ?

Actually I feel rather sorry for the dealer ...who has loaned you the kit

...did you happen to mention you knew the units would not work  I bet you did ....?

If I'd been in his place I would have had to think very carefully if it was worth the risk of loaning  the items to someone who would not be able to hear them.