On page edits, AbuseFilter defines old_content_model and new_content_model variables, containing the content model of the page (wikitext, css, javascript, etc).
Flow pages have the flow-board content model. One would expect these pages to have in AbuseFilter the old_content_model and new_content_model variables with value flow-board. But currently these variables are not defined on Flow pages.
This caused an issue on frwiki, as I had added a new_content_model == 'flow-board' condition, which could never match…