It would have been appropriate for the GA to give your original seats back to you, as you had reserved them in advance. Unfortunately, that didn't happen.
We had a similar situation but with a different outcome. We were on paid first class tickets on CO from HNL to IAH (arriving early morning) continuing on to BOS. The original booking had a 1.5 hour connection time but schedule changes reduced that to 45 minutes. Because of late inbound equipment at HNL, we departed 15 minutes late and then lost another 10-15 minutes on the way to Houston. We are now down to less than 20 minutes between flights. We exit the aircraft first and a red-coat tells us we were rebooked on a flight at 7:30 PM which was unacceptable. We ignored her and ran to the gate. When we arrived at the gate ~11 min before departure, the GA said "oh - you must be coming from Honolulu". She then escorted two people off of the aircraft and we got our seats to BOS as originally booked. I realize it doesn't usually work out this way.