I would guess that's a boarding pass that doesn't have the "DOCS OK" notation in it (whether that notation is actually printed on the boarding pass or not these days I don't know). Typically, an agent or the kiosk needs to verify your passport and check for any required visas; seems that the passport scan in the app fulfills that purpose too, but typing the numbers in does not (which makes sense; much higher probability of error and/or doing it from memory if you're just typing the numbers, whereas the scan in the app, at the kiosk, or by a human does more to verify that you actually have the passport and have all the details right).

I don't recall specifically with AA, but certainly with AS (the airline I fly internationally with most often) they have in the past issued a mobile boarding pass that requires document verification. Last I knew, AS would not issue mobile or electronic boarding passes at all for flights departing Canada (you must go to an agent), but that changes pretty frequently with AS at least.

They also typically visually verify your passport as you board in addition to the document verification. If the docs are verified before boarding, that's all they have to do at the gate. If the docs haven't been verified, they'll have to scan the passport and check the visa requirements, which would slow the boarding pass significantly if everyone had to do it at boarding.