I don't know what Canadair did, but it's specified in the regulations and I know for a fact that every Boeing jet aircraft had to demonstrate it met the 8 second requirement from approach idle during the certification flight testing. If Canadair really failed to meet the regulation, I think a major lawsuit would have put them out of business. It's certainly true that below some altitude a go-around is likely to result in ground contact (8 seconds can be a long time - ask the A320 pilot at Habsheim) but achieving go-around thrust in 8 seconds is a firm cert requirement.
I believe FADEC has done away with this, but for the 747 with the older hydromechanical controlled engines there is (or at least was) an MPD task where you needed to test the go-around accel characteristics - I think the interval was something like C-check.