Same bank. But I think all banks use the same core app of Twint, just adding their corporate identity (logo) to it.
At some point in the not too distant future, I could see a Graphene phone just becoming a secondary device or for people who do not want to use their phone for financial purposes
Indeed. And this is a pity, because you should use a secure device (like a GOS one) to do financial (and therefore sensitive) stuff.