I guess anything
is possible, meaning that "if" the top loop ever came off then you're correct, there would no longer be any tension in the lower loop. That would be true for the original single loop system as well. I suppose the shock cord could actually break... (so far no one has ever written about that actually happening) but there's no way my shock cord is going to just slip off the Eyelet Post by itself with the tension that's on it now.
To be safe I carry a spare set in my tool bag along with a few other important parts I feel I need to have "just in case". However since I installed this system I've never experienced the shock cords coming off; in fact... just the opposite
The most extreme condition so far was sailing in 3'-4' seas with a head wind of 20-30 knots; and they never budged! In this situation, my old single loop system would have allowed my Amas to bang up and down on the Akas to the tune of Giuseppe Verdi's "Anvil Chorus".
There's probably several different ways to improve on this system, each with it's own set of variables and limitations. I think for the time being I'll stick with what I've come up with.