Because macro operators apparently cannot accept arguments, the linked and non-linked versions must be separated in this way.

I don't think this is true, check e.g. keymap for node.duplicate_move macro... Think the only other example (Object one) being split is more because of historical limitations? That being said, duplicate_move and duplicate_move_linked are two different enough operations to justify having their own operators from user PoV imho, especially since we cannot give different tooltips based on settings of an operator currently. So I think it's better to have them split here too.

Nice fix, I think the use of macro operators is a good way to resolve this.

In D15086#406683, @Bastien Montagne (mont29) wrote:

duplicate_move and duplicate_move_linked are two different enough operations to justify having their own operators from user PoV imho, especially since we cannot give different tooltips based on settings of an operator currently. So I think it's better to have them split here too.

I agree with Bastien here. @Colin Basnett (cmbasnett) could you update the patch description for this?

Also I agree with Bastien's notes about the operator tooltips.

I'm getting a compiler warning:

[2481/2841] Building C object source/blender/editors/space_nla/CMakeFiles/bf_editor_space_nla.dir/nla_edit.c.o
blender/source/blender/editors/space_nla/nla_edit.c: In function ‘nlaedit_duplicate_invoke’:
blender/source/blender/editors/space_nla/nla_edit.c:1219:81: warning: unused parameter ‘event’ [-Wunused-parameter]
 1219 | static int nlaedit_duplicate_invoke(bContext *C, wmOperator *op, const wmEvent *event)
      |                                                                  ~~~~~~~~~~~~~~~^~~~~
[2841/2841] Linking CXX executable bin/tests/blender_test