That's about right, matthew - the strut failed allowing the top of the booster to puncture the main tank.
Once this had happened it's largely irrelevant what the Oxygen and the Hydrogen did. As Feynman pointed out, arguing about what happened AFTER the original failure is a bit like going over the pieces of a train wreck working out which car broke apart first, instead of concentrating on what brought it off the rails in the first place.
The root cause here was the clevis joint rotation and subsequent 'O' ring erosion. The design required the 'O' ring to expand rapidly to fill a widening gap in the clevis joint. This is NOT the way that 'O' rings are supposed to work so the design was really doomed from the beginning.
The fact that 'O' ring erosion on previous flights didn't bring them down was simply random chance and good luck, not confirmation that it was safe for this to happen.
I still can't help feeling that this sounds ominously similar to the discussion that debris had damaged tiles on previous flights. The tiles were never intended to be bashed off by bits of debris - the fact that we got away with it on previous occasions is not a good enough reason to declare that it was OK for this to happen and safe to continue flying.