Yes, I saw that, and it's been known the Sox "call the pitches" from the bench, so that's one reason I call it "staff handling" and not "pitch calling."
Vaz has gotten better numbers with the same pitchers than Swihart, but admittedly Swihart's sample sizes are very small, except with pitchers like Johnson, Pom and Velazquez.
"Weakest part of his game" may not mean weak, although weaker than hitting implies a net negative affect.