Probably not a ‘biggie’ and at least they are telling you, was just initially a little taken aback as I guess a 3rd party could access my downloads or saved payment details.
I would assume that Qobuz would have to share your e-mail with their platform partner (forum operator) to allow your account on Qobuz Club to function properly.
I would imagine that Naim would have to pass our e-mail addresses to their forum partner for this forum to function.
I guess “Circle” is something similar to “Discourse” used by Naim to host this forum. You could research Circle, and/or use the links Qobuz provides to check their privacy policy and terms of use.
I am sure that Circle wouldn’t be able to access your payment details as Qobuz would certainly have to mention it if they were relying on your agreement to conform to GDPR.
Also I suspect that no-one at Circle would have any interest at all in what downloads you had bought.