Until you crash and investigations discover how the car is being used!
Motability allow a named driver to travel to and from a permanent place of work, as the income generated is deemed to be of the benifit of the disabled person. DLM and previously RSM provide, as a minimum Social, domestic and pleasure and commuting to and from a permanent place of work. Some scheme users are also able to add business cover.
In respect of @Paul_1964 friend, using a Motability car to and from work, would be seen as generating income and therefore be to the benifit his disabled son. It becomes more complicated because they live in assisted living away from home. However, the income from work, will still benifit as it will allow parents to visit on a regular basis and also take him out 2-3 times a week.
Motability suggest you to have or to continue your lease and have named drivers, as long as you’re still getting your higher rate or component mobility allowance. The information is more clear in the previos link, I provided. What, I don’t know is how they differentiate between residential and supported living.