Sounds like functionality that is ripe for “re-purposing” by an authoritarian government.
I think the average Librem 5 customer would want to have visibility of and control over “silent SMSs”, whatever they are used for. If they aren’t used for anything then there shouldn’t be a problem in disabling them.
In the vast majority of my country the number of towers with which a phone can communicate is 0 or 1. So a customer should be safe from triangulation / trilateration out there. Of course in the cities, it is the same as anywhere else.