MOT tests for an arbitary level of emissions, whilst the "Dieselgate" issue relates to very specific levels of emissions that relate to the vehicle being classified with a certain type approval and not something your average MOT test station could be able to test for. The reason there have been issues with new car availabilty is that there are only a handful of test stations in Europe that can do the full emissions test
this software fixc is n
There hve been issues with the software used to control the AdBlue pump (had the issue on my 2.0 C7 Ultra) and the software fix is for that and not the one that changes the programming of the main ECU to remove the dodgy code that Audi/VW put in to allow the cars to pass the emissions test based on the very precise way the test was conducted and did not reflect real life