Star Alliance Gold Benefits when flying Air Canada econmy

I booked an Air Canada economy flight (with United Miles) from YUL to LAX recently. I have Star Alliance gold with Lufthansa.

I knew I would get one free bag, priority checkin/security/boarding, and Maple Leaf lounge access. However I was surprised to find:

1. Immediately after booking i could choose all preferred seats including emergency exit. I thought Air Canada didn't offer free preferred seats to Star Gold? I booked within 24 hours of departure if that makes a difference.

2. Once airborne, a crew member came to inform me I was entitled to a free meal and two free snacks. I was not expecting this either. Is this advertised somewhere?

Trying to find out what a non AC/UA Star Gold member gets on Air Canada and United can be challenging. The AI and old forum responses are frequently wrong.