It was always like that, but hey, nobody checks. I was at the ATS for new tyres before the MOT and they had a huge poster that they will refuse to MOT a car with unknown service history because the new MOT procedure adds such stress to the engine that the timing belt can go. So they were requesting proof of timing belt history otherwise they would not proceed. I have not seen this in a small garage.
But as you say, even with such notice, there will be garages that will check it out. On the other hand, it is so silly. People who have DPF problems, get some low mpg, plus being illegal, that buying a petrol car, will not only make them legal and will help them to avoid all the DPF removal costs, but they will get better mpg. I have no idea what motivated them to keep the car, remove the DPF and they did not part exchanged for a petrol one that will make them more money. At least now with the MOT, some of them will go back to petrol.