He said "without bashing the metric" of xFIP.
Perhaps you'd like to offer up your own explantion.
But be warned, saying "he's getting bad results because he sucks" is in fact bashing the metric of xFIP.
The initial question really had no answer.
Since xFIP says he's pitching fine, the only two reasons why he's getting poor results would have to be (1) bad luck; and (2) some flaw in xFIP.