Pham was the primary guy I wanted AA to get instead of Rosario, so I've done some digging into this.
The only odd thing I see is his career .858 OPS on the road vs .741 at home. That is the complete opposite of what players usually do home vs road. I mean, how likely is that something about his home stadium always suppresses his offense in 4 different home ballparks? Extremely unlikely.
My guess is there's something about his batted ball spin, like his hits a lot of knuckleballs or topspin flyballs, that isn't factored into xwOBA but does affect the actual outcomes. But he has equally terrible bad luck on grounders as he does on flyballs, so who knows.