Section 350.30(A), Exception 1 indicates that LFMC does not have to be secured within 12 inches of a box where it is fished. I generally take that to mean "old work". I am wiring a new home made with structural insulated panels (SIPs). There are wiring/plumbing chases precut into the foam core, making it possible to "fish" conduit through, but it would be very difficult to secure the conduit. Even though it is new, SIPs have the physical characteristics of old as you don't have access to the core. Do I have to secure the LFMC or is it considered to be "fished" even though it is new construction?
The Code doesn't seem to change quickly enough to deal with any new type of construction, so you have to make a judgement call.