Worth adding: "accessible" is a real-time status, not a fixed property. A station with an elevator is not the same as a station you can enter step-free today; an outage quietly takes it off the list for days, which is what those alerts are for. The data that would actually help riders is elevator status history, and almost nobody publishes it.

I check step-free routes against dated street-level imagery, and the failure mode is nearly always staleness rather than absence: a 2017 photo shows a staircase where a map said "short walk", a newer image shows a ramp the map still tags as steps. Same problem in transit, just with a maintenance crew instead of a construction crew.