it's strange ( or perhaps this the usual prominent human reaction which isn't easy to overcome).
I've felt several people ( "hybrids" ), amongst them at least two well known high-ranking Japanese, who all had a lot of internals to offer, but each and every time when challenged, their fighting spirit taking over and all internals forgotten, sheer muscling through was what was left and they were good at it.
This is why the body work has to come at the beginning of a person's training, to create a foundation that will become the person's "true nature." Whatever he has wired in, is what he will fight with under duress. It is very difficult to un-do old training and replace it with another completely different method. And, it takes a very special ability to deconstruct an old foundation and build a new one; you have to very open and willing to break yourself down to build yourself back up differently.
I suspect that those people you mention, began their training with a more conventional "external" method, and came to internal training later in their careers, adding it to their arsenal rather than reconstructing themselves with it.