I was perhaps being a lil nitpicky but still had to ask why people were questioning his core strength specifically. It isn't a concern I see on tape.
For example I see a guy like Brewer who, from what limited time we have seen him play, has bad balance and lean I would question his core strength. That may not be the problem, it could just be a coordination issue, or coaching, or any number of other issues. But having technique like Pugh's demands a strong core.
I think the distinction you make there is a very fair 1 to make. His "natural strength" needs work. The term "core strength" is becoming a popular catch phrase for strength in general, but that is why I responded because they really are not the same thing at all.