As I understand it, xFIP takes home runs out of the equation as well as defense. The Phillies have given up the 4th fewest home runs in the league. That probably helps their traditional ERA to be lower which might be a reason the difference is small between the 2 stats. We are also pretty high in unearned runs, so clearly we are not good at parts of defense. I just find it hard to believe that our fielders have decent range given the other defensive evidence out there.
We have made the 4th most errors and are tied for 21st out of 30 in team defensive efficiency.
This is not to say that defensive stats are not heavily flawed. Machado with the Dodgers is now grading above average at SS. The Dodgers probably position defenders a bit better than the Orioles but also one must think all these stats are heavily influenced by home parks and teammates (who is playing next to each other) and shifts. There is more evidence we are below average defensively than above average.