I see this often myself,I spend a lot of time on motorways as you can imagine I’m sure, and to be fair from behind you can’t tell who’s driving the vehicle in front, unfortunately though, you leave a large gap and a car or two will slot into it, especially in roadworks, I just set my cruise control to ~48mph (which is usually faster than a car speedometer be because I’m calibrated whereas they are not) and try to go with the flow....
Not to excuse the sit on the car in fronts bumper brigade (of which there’s plenty) but as I say frequently the trucker has left a safe gap but Joe car/van driver just views that as a space to jump into....