The paraminfo for flow+undo-edit-topic-summary uses the same name as that for flow+edit-topic-summary but with different content:
The paraminfo for [[https://en.wikipedia.org/w/api.php?action=paraminfo&modules=flow|action=paraminfo&modules=flow]] lists both modules and [[https://en.wikipedia.org/w/api.php?action=paraminfo&modules=flow+edit-topic-summary|action=paraminfo&modules=flow+edit-topic-summary]] also shows the data for flow+edit-topic-summary but [[https://en.wikipedia.org/w/api.php?action=paraminfo&modules=flow+undo-edit-topic-summary|action=paraminfo&modules=flow+undo-edit-topic-summary]] uses actually flow+edit-topic-summary as path and edit-topic-summary as name. I'm not sure if StructuredDiscussions is simply configured wrongly but I'd prefer if the API itself recognizes that the name/path is inconsistent (which is why I added it).
For Pywikibot this will be hard to recover from. I guess if it doesn't get modules which it requested, it will discard the data (at least the ambiguous) and request each separately to make sure it can assign names.