DVLA - For Sale Purposes - is it real?

[Leedssurveyor]

So im looking at a BMW M135i at the moment and the vendor tells me it has 1 registered owner. He is a private seller and had an C63 AMG before that somebody gave him the M135i for and some cash. He then only told DVLA it was 'For Sale Purposes' and therefore didnt have to register as an owner but only provide his information should tickets etc. be incurred. He also said his insureres have been informed of the same.

is this a real thing as I cant find any information online - but I assume this is how traders get around having to add a new owner every time they buy and sell a car?

[Leedssurveyor]

But will it affect me at all if I do buy it? Even if he is a trader? (operating from home) - he says hes not

[Leedssurveyor]

its still under BMW warranty - wont affect that will it?