This "North West" strangeness has been pushed by some in Manchester for a long time.
I read an article a while back by Hunter Davies (he of the famous Beatles biography) about when he got a job as a young journalist in a Manchester local newspaper, having grown up in what is now Cumbria. He was rather suprised that people from his local area, when referred to by the Manchester press, were described as "North West men" if they ended up in the news, e.g., headlines such as, "North West Man Attacked by Swarm of Bees", when an unfortunate from Barrow or Workington was set upon by hymenoptera.
Davies had not, until then, heard of this "North West" region and had no idea that places like Cumberland, Westmoreland and Furness were a part of it.
Back then - and the man is pushing seventy now, and so this is decades ago - he recognised it as an empire building notion by a big city, trying to claim all adjacent areas as part of a region centred on itself.
It's a bogus region - you only have to visit Carlisle, which looks, sounds and smells much more like its relative neighbours, Newcastle and Durham, than far off Manchester and Crewe to realise this. Or spend a night drinking in Wrexham or Prestatyn when there's a Liverpool match on tv - scores of men in red jerseys, Scouse accented native locals cheering when the goals go in - this outer fringe of Liverpool's city region not being included in Manchester's idea of its "North West" region - a region some would try to have us believe Liverpool is a part of.
If Lancashire milltowns like Preston want to adopt a secondary role within a region focussed on the big daddy of Lancashire milltowns, Manchester, which has always been the centre of this rather more tightly-focussed but more natural region: industrial, milltown Lancashire, that's up to them. After all what are Preston, Blackburn and Burnley but smaller, less successful versions of Manchester?
But Liverpool and rural Cumbria aren't, and won't ever be, part of this region.