The point is valid, but irrelevant. If what has been reported is true, than BP is fully responsible for the leak. The company man over-ruled the tool pusher in an argument over what technique to use to finish the well. BP chose not to use some expensive but recommended additional valves.
Secondarily, Transocean, because the BOP was faulty - that is the responsibility of the drilling contractor and the tool pusher.
No, BP is not responsible ~ the FEDERAL GOVERNMENT owns the well. BP drilled it, but pays royalties to continue to use it.
The inspection regime created and administered by an army of EPA, INTERIOR and special interest lawyers proved to be inadequate.
In the future the "experts" should call in capable statisticians and quality control experts to ADVISE them on what to do, and what not to do. While they are being instructed the lawyers shold be tied and gagged!
Checking off boxes on a punch list won't do the job when it comes to a complex structure like an oilwell in the middle of the Gulf of Mexico at over a mile deep.