I would be in favour of a silent alarm so long as the building is of the correct standard, which this sounds like it is, or will be. If it is stay-put then the people are clearly better off not knowing to avoid the situation you point out, people investigating what is happening and potentially putting themselves at risk.
In the sheltered housing, to control 'unwanted signals', if the system is addressable then the receiving station could know the difference between an alarm in someones dwelling, and a second knock in the communal corridor. The latter clearly warranting an attendance by the Fire Service. (The prior still warranting investigation via telephone at least)
I am also in agreement with Kurnal regarding the tower blocks. Bear in mind that any detection already in place may also operate some vents, depending on the layout of the building.