My thought would be that based on the fact that high 4sFB typically get less ride, the Z break that Mahle is getting in those locations is absurd.

Good guess but no.

while Jake Burger, JD Martinez and Jose Altuve tend to remain more closed.

In contrast, Aaron Judge does not gain much ground with his front foot from release to intercept, though his foot is farther forward than in his batting stance.

...

791894 baseballsavant.mlb.com/gamefeed?dat...

I also think that a significant part of a secondary’s effectiveness remains its synergy with the FB (which is obvs baked in to models as well) and a hypothetical “expected” movement profile might coincide with higher synergy.

for INTL pitchers (the timeline is also stretched thin for INTL position players) and perhaps a domestic reserve exception as well. The goal of MLB should be to maximize the talent on the field and INTL pitcher success is a clearly necessary area for improvement.

Some of this disparity is likely due to demographics (for instance, height tends to be emphasized for SP and the Latin American population is ~0.4 SDs shorter on average) and other factors. However, it does seem like MLB as a whole can do more to ease INTL pitcher dev, like increasing R5 time...

Sasaki seems relatively similar to Senga imo. His splitter is devastating (like the ghost fork) but he badly needs another in-zone weapon if his 4sFB gets tagged. Senga developed an improved cutter that was the key to his 2023 success. Roki will likely need a pitch of that ilk.