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 #Flow 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-core 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.