addressing PR comments

Author: smithto1

pandas/core/groupby/generic.py

@@ -1826,9 +1826,7 @@ def count(self):
 
  # If we are grouping on categoricals we want unobserved categories to
  # return zero, rather than the default of NaN which the reindexing in
- # _wrap_agged_blocks() returns. We set self.observed=True for the call to
- # _wrap_agged_blocks() to avoid it reindexing. We then reindex below with
- # fill_value=0. See GH #35028
+ # _wrap_agged_blocks() returns. GH 35028
  with com.temp_setattr(self, "observed", True):
  result = self._wrap_agged_blocks(blocks, items=data.items)
 

pandas/core/groupby/groupby.py

@@ -1537,9 +1537,7 @@ def sum(self, numeric_only: bool = True, min_count: int = 0):
 
  # If we are grouping on categoricals we want unobserved categories to
  # return zero, rather than the default of NaN which the reindexing in
- # _agg_general() returns. We set self.observed=True for the call to
- # _agg_general() to avoid it reindexing. We then reindex below with
- # fill_value=0. See GH #31422
+ # _agg_general() returns. GH 31422
  with com.temp_setattr(self, "observed", True):
  result = self._agg_general(
  numeric_only=numeric_only,