But are they actually more diverse than the average team that way? Anecdotally it seems like there is a deeper pool of Latin relief pitchers and bench players (and probably catchers too).
A lot of different factors involved, including concidence, to where the Phillies have been able to compensate for their poor internal development via trade or free agency, and younger cheaper Latin players have come via the former avenue, with expensive white players coming via the latter (except for Walker). Some of the Latin players were also not yet developed (Alvarado, Sanchez).
Separate from race, Walker and Casty and Luzardo were all domestic players (and English speakers). Obviously the Phillies seem to support their Latin players well (with Veladia at the top and a full-time translator. Five of the 12 major league coaches now are also Latin). The low number of starters is more about failing to develop enough of the signings.
I think the main reason the Phillies would do well to just have a Japanese player of any kind would be as a reason to lay the foundation of a support system, and set an example, for the next guy. They took a wild roll of the dice at that last year with the reliever, then quickly found out why no other team wanted him.