Revert "PERF: Delete flag for sorting multiindex loc call."

This reverts commit 7fee53c.

Author: nrebena

pandas/core/indexes/multi.py

@@ -3103,6 +3103,21 @@ def _reorder_indexer(
         -------
         indexer : a sorted Int64Index indexer of self ordered as seq
         """
+        # If the index is lexsorted and the list_like label in seq are sorted
+        # then we do not need to sort
+        if self.is_lexsorted():
+            need_sort = False
+            for i, k in enumerate(seq):
+                if is_list_like(k):
+                    if not need_sort:
+                        k_codes = self.levels[i].get_indexer(k)
+                        k_codes = k_codes[k_codes >= 0]  # Filter absent keys
+                        # True if the given codes are not ordered
+                        need_sort = (k_codes[:-1] > k_codes[1:]).any()
+            # Bail out if both index and seq are sorted
+            if not need_sort:
+                return indexer
+
         n = len(self)
         keys: Tuple[np.ndarray, ...] = tuple()
         # For each level of the sequence in seq, map the level codes with the