It doesn't really matter does it? The point was that a problem was identified and that that same problem likely exited (depending on when the shells were manufactured) on the Washington as well.
Well, it is more complicated than that.
Mass fired quite a lot of shells against battery El Hank, situated inland. If the US forces managed to study unexploded 16" shells, they most surely were found around battery El Hank.
Now, the AP shells in general had the tendency to not explode at all. This is because the way they were designed - to first perforate a given amount of steel, and than to travel some distance, and only after that to explode. [remember the 15" hit on Prince of Wales con tower, or the 14" hit on Bismarck;s forecastle - the shells simply did not find enough armor to fuze - deceleration rate was to slow] So, first the fuze must be initiated, "timer" started, and only after the time delay passed would the filler explode. US 16" AP shells for instance had an average of 0.033seconds fuze delay.
The shells interaction with armor plate was different from the interaction with the ground [as this appears to be the case].
Thus, I don't think any aspects can be inferred to ship-to-ship capabilities, especialy as Massachussets fired very well against several naval targets that day, against which the shells performed exactly as expected.