This,
BABIP (by definition) does not include HRs. The advanced pitcher metrics all include some form of HR rate. So, the advanced metrics (DIPS, FIP, etc.) should all be (to some degree) capturing batted ball speed, since HRs are easily going to be the highest spike on the ball-speed chart.
So, I'm not sure how ground breaking this is
Well, they "include" HR rate in a very poorly-targeted manner. It's like saying ERA "includes" doubles, or OPS "includes" walks. The question is how well a stat isolates component skills.
xFIP, for example, "includes" homers -- only to "normalize" them. To xFIP, a homer is no more and no less than ... one more fly ball.
Not sure how FIP captures batted ball speed any better than ERA captures it. Sure, FIP makes a pass at batted ball speed by saying, "well, 4% of the BIP's went over the fence." But that's as far as it goes. Not very useful, especially since sabes believe that the 4% figure was random and luck-driven.
............
The groundbreaking part of the MPH paradigm is that the IF/F, LD, and HR/FB categories are so vague and inaccurate. Actual pitcher performance is clearly blurred by the noise. When a blooper is scored a line drive, that's noise. When a 50 mph clonker is scored a GB just like an 85 mph one-hopper is scored a GB, that's noise.
What is inaccurate about MPH, though? The split-half correlations were perfectly sound.