Fidelity's cash-management activity export puts the payee in the Action column (DIRECT DEBIT CHASE CREDIT CAUTOPAY (Cash)) and writes No Description in Security Description. ai-bookkeeper took the latter, so all eleven rows in a sample export came out as the same words and the categorizer had nothing to learn from.
Reading the example exports in redstreet/beancount_reds_importers (read only, nothing copied) also showed that the all-accounts Fidelity file's buys and dividend reinvestments were booked as spending. Both now follow what Schwab brokerage files already did: the Action text is the description, and YOU BOUGHT, YOU SOLD and REINVESTMENT lines are skipped with a note, while dividends, interest and transfers are booked.
The test uses rows made up in those two layouts. These are open-source test files, not a real person's account, and the dividend-reinvestment treatment (dividend booked as income, reinvestment skipped) mirrors the Schwab reader rather than a Fidelity statement.