Ken, what loma is saying is that the failure would happen at about the same engine clock position - not the fan clock position (which as you noted is constantly changing as the fan rotates).
There a inlet probes in front of the fan for total temp (and on EPR engines, total pressure) - these create turbulence/vortices. The big concern for these has been the fan hitting those vortices makes a lot of noise - hence on new installations those probes have been pushed further forward in the inlet to give the airflow a chance to clean up before it hits the fan. What lomapaseo is pointing out is that those probe vortices also cause a once/rev stress on the individual fan blades as they pass - so if there is a cracked fan blade, it is most likely to fail as it passes through the probe wake.
I saw the report on a real severe case of this once/rev stress. A brand new GE90 (I think, it's been ~20 years) came apart during acceptance testing. Turns out part of one of the fuel nozzles hadn't been installed properly and came loose - it moved through the burner and blocked one of the stage one turbine nozzles. So first stage turbine blades saw a massive once/rev stress as they were totally unloaded then reloaded as the passed the blocked nozzle. It took something line 10 minutes at power before the first turbine blade failed
