If these lines were working within their safe working load this would be a fair point.
Yes a missing parallel working line is a double load on the remaining line and more in the dynamic. 1 line missing from 6 might be up to a doubling of dynamic loading. Each line in the TRPT sets I’ve flown has been rated for over the full load measured. So that’ll be well within limits.
Also
In turbine control we’re trying to avoid ever getting near to overloading the system.
Spilling wind, raising elevation, yawning, contracting, landing…
But inevitably, shit goes wrong, bad things happen. When it does. Best to have a planned ready backup.