You'll find BMW, JLR, Nissan, Toyota and Ford shut down their plants in the UK during summer just like the others.
It's an engineering thing, not a 'car production' thing. Those who sit behind desks fail to understand these things, I guess. Bear in mind that a car factory will have upwards of 5000 people working in them, bolting together cars. So those people who screw dashboards in, screw dashboards in. If there's no dashboard screwer, then no dashboards are screwed in, and production stops, therefore you get the whole factory full of assembly workers to **** off on their summer holidays, then they come back fresh and make good cars again.