The contributing strings should be lower on the curve, so they below after the shorted string; 7 strings really does put you at a critical point compared to say 2-3 strings in that you hit instantaneous range on the damaged string faster. Once you start arcing, the fault switches to a high impedance as well, reducing the chances of being "saved" by the contributing string fuses.
We also don't know for sure if a single cell failed short or if multiple cells had dendrite issues which could escalate the issue under heavy load-- higher resistance but more cells impacted. Possible it is related to the original damaged string with one cell replaced.
That is how I saw it as well; it is possible there were two failures before the fuse blew (and we will never know for sure): inverter fault, current surge on the battery stresses one (or more) marginal cell(s) fails leading to a short, and finally the fuse tries to clear the fault.
I guess the thing needing additional information is the frequency of catastrophic cell failures. I had assumed for LFP it was less than 1:10,000,000 over a 10-year calendar life.