diff --git a/e3sm_diags/e3sm_diags_driver.py b/e3sm_diags/e3sm_diags_driver.py
index 111d20f0db..f99d6422bf 100644
--- a/e3sm_diags/e3sm_diags_driver.py
+++ b/e3sm_diags/e3sm_diags_driver.py
@@ -354,8 +354,9 @@ def main(parameters=[]):
 
     # If no parameters are passed, use the parser args as defaults. Otherwise,
     # create the dictionary of expected parameters.
-    if not parameters:
+    if len(parameters) == 0:
         parameters = get_parameters(parser)
+
     expected_parameters = create_parameter_dict(parameters)
 
     if not os.path.exists(parameters[0].results_dir):
diff --git a/e3sm_diags/parser/core_parser.py b/e3sm_diags/parser/core_parser.py
index 2d1defd23b..169eaf0072 100644
--- a/e3sm_diags/parser/core_parser.py
+++ b/e3sm_diags/parser/core_parser.py
@@ -784,8 +784,7 @@ def get_cfg_parameters(
         RuntimeError
             If the parameters input file is not `.json` or `.cfg` format.
         """
-
-        parameters = []
+        params = []
 
         self._parse_arguments()
 
@@ -801,10 +800,7 @@ def get_cfg_parameters(
                 else:
                     raise RuntimeError("The parameters input file must be a .cfg file")
 
-                for p in params:
-                    parameters.append(p)
-
-        return parameters
+        return params
 
     def _get_cfg_parameters(
         self, cfg_file, check_values=False, argparse_vals_only=True
diff --git a/e3sm_diags/run.py b/e3sm_diags/run.py
index df541319a3..e669b032f2 100644
--- a/e3sm_diags/run.py
+++ b/e3sm_diags/run.py
@@ -66,42 +66,34 @@ def get_final_parameters(self, parameters):
 
         self._add_parent_attrs_to_children(parameters)
 
-        final_params = []
-
-        # Get the sets to run using the parameter objects.
+        # Get the sets to run using the parameter objects via the Python API
         sets_to_run = [param.sets for param in parameters]
         self.sets_to_run = list(chain.from_iterable(sets_to_run))
 
+        api_params = []
         for set_name in self.sets_to_run:
             # For each of the set_names, get the corresponding parameter.
-            param = self._get_instance_of_param_class(
+            api_param = self._get_instance_of_param_class(
                 SET_TO_PARAMETERS[set_name], parameters
             )
 
             # Since each parameter will have lots of default values, we want to remove them.
             # Otherwise when calling get_parameters(), these default values
             # will take precedence over values defined in other_params.
-            self._remove_attrs_with_default_values(param)
-            param.sets = [set_name]
-
-            other_params = self._get_diags_from_cfg_file()
-            params = self.parser.get_parameters(
-                orig_parameters=param,
-                other_parameters=other_params,
-                cmd_default_vars=False,
-                argparse_vals_only=False,
-            )
+            self._remove_attrs_with_default_values(api_param)
+            api_param.sets = [set_name]
 
-            # Makes sure that any parameters that are selectors
-            # will be in param.
-            self._add_attrs_with_default_values(param)
-            # The select() call in get_parameters() was made for the original
-            # command-line way of using CDP.
-            # We just call it manually with the parameter object param.
-            params = self.parser.select(param, params)
+            # Makes sure that any parameters that are selectors will be in param.
+            self._add_attrs_with_default_values(api_param)
 
-            final_params.extend(params)
+            api_params.append(api_param)
 
+        # Get the diagnostic parameter objects from the .cfg file passed via
+        # the -d/--diags CLI argument (if set). Otherwise, it will be an empty
+        # list.
+        cfg_params = self._get_diags_from_cfg_file()
+
+        final_params = api_params + cfg_params
         self.parser.check_values_of_params(final_params)
 
         return final_params
@@ -248,14 +240,14 @@ def _get_instance_of_param_class(self, cls, parameters):
         raise RuntimeError(msg.format(class_types))
 
     def _get_diags_from_cfg_file(self) -> Union[List, List[CoreParameter]]:
-        """Get diagnostics defined in a cfg file using ``-d`` CLI arg.
+        """
+        Get parameters defined by the cfg file passed to -d/--diags (if set).
 
         If ``-d`` is not passed, return an empty list.
         """
         args = self.parser.view_args()
         params = []
 
-        # If the user has passed in args with -d.
         if args.other_parameters:
             params = self.parser.get_cfg_parameters(argparse_vals_only=False)
             # For each of the params, add in the default values