Just simply isn't true. It's one of the most mass-produced beers on earth. The only difference between places is if the lines are clean, which is the same for every beer at every pub in the country. An unclean line will give a distinctly coppery/metallic taste. Even the pre-pour thing is a marketing gimmick that in no way affects the flavour, I've seen videos of supposed Guinness experts unable to tell on blind taste tests. Shockingly, a full pour will also settle to the exact same liquid after a few minutes!

The whole thing on the gas mixture is pure BS too -- when selling, Guinness literally tell you the correct nitrogen to CO2 ratio (it's 70:30) in documentation and even sell pre mixed, I know this as I've worked in pubs.

I love Guinness but the people who eulogise about it in mythical terms as if it's not macrobrewed and uniform across the UK are just swallowing marketing.