This subject has been raised several times before to no avail. Either no one at BT takes note of these forums or they are just not interested in customer feedback.
Presumably you are watching on a Canadian station which is taking the Bt Sport commentary. Given that the concurrent matches are not being shown in full on BT Sport rather only available in a highlights program much latter in the evening I suspect that there are UK rugby fans who appreciate updates on their team match as well as some who prefer to focus on the game in hand. Perhaps a solution for you is to actually watch the games you record in a different order so you don't watch the BT Sport main game until after the other matches.