While looking for some info on his signing bonus, I came across the press conference covering his signing that features A.J. Preller.
Some quotes from the presser can be found here and here.
Kid is apparently 6.3 and somewhere in the 177-192 range with good command and mechanics, a FB in the 88-90 range, a good changeup, a curve (and messing with a slider). He will likely be the youngest guy in the system next year at 16.8 a/o 4/1.
Missed this report a couple of weeks ago: Arredondo had TJ surgery last July, shortly after signing.