He's practicing something to overemphasize a feeling that shows different results in real use. My golf instruction has had some similar stuff, I do a drill hitting half driver hooks on the range but in action it becomes a low (for me) fade. I assume he wants to stay on top of the high fastball, lest he hit all pop ups. Derosa on MLB network did a feature about Miranda and his hand positions the other day. It's all about the high fastball, the pitch in vouge to counter the fly ball era.
Any trend comes to a logical oversaturation and diminishing returns. High fly balls are outs almost as often as ground balls but only because of more ground to cover. The money has always been in a line drive. Add in the shift restrictions and it evens out a bit.
I've never thought the Popkins way was similar to what Donaldson describes, despite TD lore. Correa is doing what good hitters do, work the at bat and hit what you're given. Sometimes it's a pitch to turn on, sometimes you go the other way.