Can someone explain WHY this new UK (England, Wales, Scotland and Northern Ireland) passport regulation has been introduced?

https://www.bbc.com/news/articles/cx2d9yk2kpjo

I've been having some difficulty posting this. Although I think it definitely has something to do with the United Kingdom it was rejected and deleted by r/unitedkingdom. I then thought to try r/AskUK - but the same happened. So as a last resort I will try r/LegalAdviceUK

This has just hit my Canadian cousin who was inconveniently born in Edinburgh before emigrating to Canada at the ripe age of 3. He has never held a British passport, back in 1957 children travelled on their parents passports. He has been to Britain multiple times as a Canadian citizen on a Canadian passport.

So he booked an Arctic Cruise for his wife and himself out of Amsterdam and up to the North Cape and back via Aberdeen, where a six-hour stay is planned. And he has now been told by the cruise company that he will not be allowed to land or he can pay gazillions of Canadian Loonies to get an expedited UK Passport which he will almost certainly never use again.

He, and I, just want to understand why? After 70 years of him occasionally travelling forth and back, what changed. Well, we know what. But why did it change? Is this just a bureaucratic money-maker for the Home Office? Help.

BTW - He decided to sit out the stay in Aberdeen on board the boat.