Based on some of the comments from the surveys it would appear there are two problems.
The first is the perception of some including many young drivers that the truck races them to the roundabout. What the truck driver is trying to do is join the traffic flow and still be moving on entering the roundabout. This situation, of course, isn’t always possible, but when achieved the benefit is to all vehicles. Remember trucks cannot accelerate like cars. Should the heavy vehicle be forced to stop at the last second then,, all traffic is delayed while the truckie selects a low gear and moves off. A loaded B-Double of up to 64.5 tonnes gross proceeds steadily and due to the length sometimes no other traffic can proceed until the truck is gone.
The second problem linked to Tip 2, the “DO NOT OVERTAKE TURNING VEHICLE” signs. Again due to the size of many roundabouts and the length of semis and B-Doubles it is often impossible to travel through, let alone turn, without using more than one lane. If you stay back behind the truck and heed the signs, you won’t end up in a blind spot or get hit by the trailer as it travels through or turns.