Im not sure I agree with that analysis. Sounds more like an argument to suit a narrative.
Does temporary employment increase travelling distance.
People havent worked in their local town for many decades.
What about increased opportunity for people to work from home
Or conversely the exponential rise in internet shopping -how many diesel vans are delivering? What difference would it make to the number of journeys whether the drivers are on zero or full time contracts.
Perhaps we should be point the finger at VW for lying about emmisions.