3 seconds is the minimum safe distance, regardless of speed
This is just plain untrue.
In all cases you need to drive to the conditions. Observe your circumstances and adapt your behavior accordingly.
3s is a good yard stick, but there’s plenty of situations in which it is not the ideal safe distance.
At 110km/h that’s about 90 metres. Every idiot around is going to try to move around you to take up that spot. Being overtaken by idiots is unsafe. This is just one example, there’s plenty of others.