From reading the white paper, it sounds like they are saying the circuit breaker could open, the control circuit is not powered but somehow the coil remains powered and burns up.
In a grid tie situation using grid clocked inverters there is no situation where the line side voltage will be significantly lower than the load side voltage and you will not have a situation wnere the control circuitry of the XFCI is not properly powered .
This is not what we normally consider back feeding where the line side of the breaker remains hot with the breaker open.
