Valve mentioned that in practice packets are dropped about 5% of the time, so two connections might theoretically reduce that to 5%^2, or 0.25%. Meaning out of every 1,000 seconds of playtime, only 2 seconds would be disrupted rather than 50s.

It seems unlikely to be as clear-cut as this, since two connections from the same host to the same endpoint will probably use the same route to get there. So why would using two connections avoid retransmission? But it's worth checking whether it works.