It's the first I've heard of a bank admitting why.
I've had a few clients that have had their bank accounts closed with no explanation as to why. Just a "we're ending our banking relationship with you" letter. If they ask why they just say "We won't tell you, you can't appeal, our decision is final", which is incredibly frustrating!
Neither of the clients I know this happened to are dodgy, or would have said anything out of turn and certainly aren't in the public eye, so I still have no idea to this day why they closed their accounts.
At the end of the day, a bank doesn't have to do business with you, just like if you run a shop you don't have to serve everyone that comes in. You can refuse service to anyone you don't want to serve.
It doesn't sit comfortably however, for the banks to admit to closing bank accounts just because of something a customer has said.
With Nigel Farage, it's because he's a Politically Exposed Person and therefore is deemed to be much higher risk, but I bet they're not closing down Rishi Sunak's bank account!