hook_inline_entity_form_entity_form_alter isn't called when inline entity form is "complex"

I've got a number of inline entity forms set up for storage entities. Six out of seven of the forms are set to "simple", with one being "complex".

In a module, I've got my_module_inline_entity_form_entity_form_alter added and I've added a call to Drupal::logger. Looking at dblog, it only shows 6 lines of debugging code unless I change that complex form to simple.

Is there a different hook for complex forms or is something else amiss?

Thanks!