ai-bookkeeper reads bank CSVs without asking the user to map columns. For N26 it only knew the current English header (Booking Date, Value Date, Partner Name, ...). N26 exports in the language of the app, so a German or French account got the generic reader.
The generic reader already got dates and amounts right on test files, so nothing was lost silently there. What was missing: the files were not recognised as N26, and a Partnername header would have left the payee out of the description.
Both are fixed. The three other column lists come from the header tables of the open-source beancount-n26 importer; the test files are made up. No real N26 export has been tried, so a download that differs is the next thing to check.
Along the way the Revolut column list was cross-checked against a second, independent importer (tarioch/beancounttools) and matches.