"a matter of national security" - there are endless interfaces into the network (by law) for lawful interception and some of them are designed in such a way that Interceptor E1 cannot see what Interceptor E2 is trying to read.

Still, some 'other' interested parties that have reasons not to use the standardised interfaces.

For 5G at lot of additional security measures CAN be enabled, but you can guess who started to complain about that.