A FlyerTalk Posting Legend
Join Date: Sep 2012
Location: SFO
Programs: AC SE MM, BA Gold, SQ Silver, Bonvoy Tit LTG, Hyatt Glob, HH Diamond
Posts: 44,353
You arrived at T-5, which is 10 minutes after the boarding gate cutoff.
It sucks, but holding a plane isn't what I'd expect a concierge to do. I'd expect them to meet me, say "you've missed the flight, but we have you rebooked via XXX". If that was not offered, that would be my complaint.
While different people have various risk aversion to low connection times, you booked a legal connection, and as such, it's AC's responsibility to get you to your destination.