The fine details of implementation are not noted so we can only speculate. I would hope it's designed to very gradually start limiting the speed after X seconds of alerting the driver. That said, even the most naive design, which would work the same as RPM limiters (which all cars have to avoid engine damage) would just cut fuel injection whenever over the limit. This produces about the same effect as coasting in neutral, so even then you are going to coast to a stop very very gradually and have lots of time to make it to a shoulder.
That said, even that does present some danger -- not to me or you of course, but you know, to shitty drivers who might not be accustomed to driving cars that fail at random and might panic and fail to cope appropriately with the situation. I mean, I have even ridden with drivers who are afraid to stop on the shoulder, even in a situation that warranted it, so it's bound to happen now and then. A manual override if available, will help here, but the pool of drivers dumb enough to still be startled into making a mistake will merely shrink then, not disappear.