BUG: Fix unexpected sort behavior on aggregation

Author: Licht-T

pandas/core/generic.py

@@ -6631,7 +6631,7 @@ def pct_change(self, periods=1, fill_method='pad', limit=None, freq=None,
         return rs
 
     def _agg_by_level(self, name, axis=0, level=0, skipna=True, **kwargs):
-        grouped = self.groupby(level=level, axis=axis)
+        grouped = self.groupby(level=level, axis=axis, sort=False)
         if hasattr(grouped, name) and skipna:
             return getattr(grouped, name)(**kwargs)
         axis = self._get_axis_number(axis)