"
....but when you have 3 of something performing one function that all have to work then what do you call that? You need a new category Triple Fault Intollerant perhaps?"
AnFI- in terms of FMEA the 3 tension struts are not performing the same function. Each one is performing a separate function, but they are part of a common system. Since an individual tension strut will experience total loss of function due to a single (structural) failure event, the tension strut itself has zero fault tolerance for this failure mode. And since the MRGB attachment system will lose the capability to perform its function due to the failure of a single tension strut, the MRGB attachment system also has zero fault tolerance for the failure mode. If the tension strut and MRGB attachment system perform a critical function required for safe flight and have no fault tolerance for this failure mode, it must be shown by analysis that the failure mode is an "extremely improbable" event.
Here's a relevant section from FAR 23.1309:
"(c) The airplane systems and associated components considered separately and in relation to other systems, must be designed and installed so that:(1) Each catastrophic failure condition is extremely improbable and does not result from a single failure;
(2) Each hazardous failure condition is extremely remote; and
(3) Each major failure condition is remote."
If you have an interest in learning more on the subject I recommend reading
FAA AC23-1309-1E. It's not specific to rotorcraft, but the basic principles still apply.