More evidence of BP’s “go cheap at any cost” approach.
But really, I think the question of madifications to the BOP is moot, if you look at the post just before yours.
It wouldn't have mattered if it had been rebuilt by Cameron with the direct nit-picking supervision of the Board of Directors, it wasn't designed to operate with two strings in the hole.
It appears the following contributed to the disaster:
Failure to assess the negative pressure test results on the plug as showing a leak.
Displacing the riser without remediating that leak.
Failure to act upon increased returns (volume) while displacing.
Failure to act on the well continuing to flow while the pumps were shut down.
Continuing to displace the riser despite indicators of a kick in progress.
(PLEASE NOTE: I am not pointing any fingers at anyone in particular. It has not been ascertained who did or did not notice or act or attempt to act (or even order otherwise should that have happened) in the instance of the apparent indicators above, that will (possibly) be revealed by inquiry later, and I am not pointing any fingers at anyone on the crew or in management without the facts, be they living or dead. That will get its day in court, and I await those findings.)
Possibly, at the time of the explosion or thereabouts, it appears a length of drill pipe was knocked/dropped in the hole, next to the string in the riser. It appears that pipe wedged in the riser at or near the base, having at least partially entered the BOP stack.
When it rains, it pours, but no pipe rams will seal over two strings, the annular can't wrap around that either and seal, and blind rams only close over open hole. The shear rams were likely not rated to cut two sections of drill pipe simultaneously.
At that point, it really does not matter where the BOP was serviced.
You don't blame the A&P because your Spad won't do Mach 2, either.