Refinements

Author: rhshadrach

pandas/core/groupby/groupby.py

@@ -4440,6 +4440,7 @@ def post_processor(
 
         ids, ngroups = self.grouper.group_info
         if self.dropna:
+            # splitter drops NA groups, we need to do the same
             ids = ids[ids >= 0]
         nqs = len(qs)
 

pandas/core/groupby/ops.py

@@ -998,10 +998,11 @@ def apply_groupwise(
     # Methods for sorting subsets of our GroupBy's object
 
     @final
-    @property
+    @cache_readonly
     def _sorted_ids(self) -> npt.NDArray[np.intp]:
         result = self.ids.take(self.result_ilocs)
         if getattr(self, "dropna", True):
+            # BinGrouper has no dropna
             result = result[result >= 0]
         return result
 

pandas/core/reshape/pivot.py

@@ -717,8 +717,6 @@ def crosstab(
         margins=margins,
         margins_name=margins_name,
         dropna=dropna,
-        # TODO: Not sure if this is okay
-        observed=dropna,
         **kwargs,  # type: ignore[arg-type]
     )