In fact the person makes any number of mistakes and either flat out lies or is, to put it politely, completely misinformed about any number of things.
The main issue is he using one dealer and one carline. Different dealers and manufacturers have come a long way in the last few years streamlining the buying processes. As far as marking up vehicles…. The manufacturers do not condone it and some will punish franchisees for doing so. With that being said , it’s still supply and demand. If you insist on buying a vehicle during a supply chain crisis you may not get the car you want. I’ll assume the same applies the the UK as well. I doubt Nissan is allotting a surplus of cars for England and leaving dealers here with empty cupboards.