I wonder is there a similar thing going on with modern baseball vs the old school stuff like above. Both of those swings look far more into the lead side than the modern ones that really do hang back big time as you say. Particularly Ruth above, it looks a much more completed golf swing style action. You’d never see that completed full rotation all the way through/around these days - at least not from the baseball I’ve watched, which isn’t a lifetime of it by any stretch.
Their starting point with the bat seems much lower/shorter to my eye too - is that fair to say? The modern swings seem to have their hands up above their back ear when waiting for the pitch? I’m sure that plays a part in the under and up hang back swing, as opposed to this flatter, more driven strike through the pitch that Ruth and Gehrig seem to be doing.
