It’s not a sidewalk. It’s a railroad track for the VTA train in San Jose. FSD has no idea it’s not a drivable area. Guess what other technology Tesla has shunned that would’ve completely eliminated this issue? HD maps.
The pole literally has pedestrian buttons on it. I'm fairly certain that humans are intended to push them. Maps might help, though!
Street View [1] shows it's a railway track. The car didn't figure out it was one.