MEANING OF THE CLASSIFICATION

First of all, and needless to say, those who were classified into puncher or swinger type by me didn't know my theory. It means that they built their hitting mechanics without understanding the difference of these two types. Therefore, some hitters are on the middle point between the both types, and other hitters might change  their mechanics from one to the other. However, great hitters and good hitters who has or had earned good stats solidly among long-term can usually be classified into one specific type obviously. This fact based on my observation made me sure that being either specific type throughly was very important regardless which type the hitter choses.

However, there certainly had been the "regime change" from the swinger type to puncher type in the MLB. So what caused the change? While there are many possible causes I'm inferring, it would be the primary one that the pitching skills have been advancing, especially regarding the breaking balls and moving fastballs. Probably, the struggling to adjust against more hard pitches would produce the change of hitting theories and the way of instructions, as well as players' hitting mechanics. In fact, so many hitters have come to adapt more compact mechanics, short stroke swing, and relatively light bat, which would reflect their attempts to overcome outstanding pitchers having rich arsenals.

Anyway, the "revolution" of hitting mechanics is assumed to have been brought by those simple and practical thoughts, not by academic and biomechanical theory. Therefore, the change is often vague, and transition of it appears to be unobserved mostly. For example, let's see the following movie, 1989 WS game3, and focus on Jose Canseco(~0.56) & Garney Lansford(~1.51). Both of them adopts the similar batting stance, rhythm motion, and small stride. But, their swings look quite a bit different.



Wile Jose Canseco's swing often lacks the arm extension like Barry Bonds and Derrek Jeter, Lansford's swing seems to be somewhat classical one. In short, Canseco is a puncher type hitter, and Lansford is a swinger type hitter.

Here is the side view of Canseco's home run swing which lacks arm extension. It doesn't necessarily mean his muscle strength.