I only have to consider my own mind at different times to realise how complicated a question this is. Who is a true believer? Who really has no doubts? In some ways the nature of true belief is to have doubts. Because to take anything seriously involves thinking about it deeply.
Which perhaps raises another question. Are there any on the GB who don’t take it seriously? I don’t think there are real signs of that. (Compare some TV evangelists where the signs are rather obvious) There do seem to be genuine signs of mental fatigue from a couple of members, in particular I think of Loesch and Herd. They no longer appear as confident or enthusiastic as they once did. Their early exuberant support of the organisation and its mission may have mellowed into some form of accommodation rather than outright cynicism.
They all have personal lives, and health issues, and families, and mundane organisational issues and other things that occupy their minds. I would not be surprised if big picture questions about truth and the nature of the religion they oversee is mostly crowded out by other concerns.
One thing I’ve become increasingly aware of is the ability of people to avoid thinking about things that, from the outside, it seems should be a serious concern. People on the whole are not terribly reflective, especially if reflection would interfere with getting on with life in a way they find immediately comfortable.