Never had an issue with RSI misinterpreting a speed limit - but the roadsign speed adjustment was on (by default..) when I first took possession of the car and boy I'll tell you I was scared sh!tless when it kicked in the first time (as I was approaching a road toll boot doing 130kph it abruptly slowed down to 60kph
) That's when I disabled it and it's been off ever since..
You would think that it would use navigation speed info to adjust the speed gradually- but nope- it will just hit the brakes for you when it sees a sign..