It also could have been a sandwich left in the LOX tank, or malware planted by Nigerian scammers. If you don't accept the information provided by the relevant parties then the possibilities are basically unlimited. That's not to say that you must accept what they say, but if you don't then why would you focus on this particular possibility out of millions?
The strut failure is consistent with the data, and the accepted conclusion of the report.
They are modifying their procedure because their prop loading procedure was _very_ aggressive (pumping liquid helium into the COPV and allowing it vaporize, absorbing more heat from the environment, resulting in the formation of solid oxygen). They exceeded the tolerances of the COPV, and paid for it. In the future their designs will account for the lower temperatures. Until then, switching to the more conservative prop loading method addresses the issue.
The strut failure is what SpaceX reported but it could have also been a COPV explosion.
Two confirmed COPV explosions and a third possible explosion. SpaceX itself mentioned that an improved design will be done in the future because they had to modify their fueling schedule to increase the safety margin in the things.