I agree, I think Bruce had elevated his understanding to the level where he was in a position to leave the idea of systems & styles behind.. If he was guilty of anything I think perhaps it was that he expected too much too soon from his students, who on the whole hadn't gone on the journey of discovery that he had.
Obviously that observation doesn't apply to some of the already veteran martial artists he trained with such as Dan Inosanto, but to people like Steve McQueen & James Coburn I think it was perhaps too much of a leap..