Boils my piss frankly. In any other walk of life that would be called a conflict of interest. But it's all in the member's register of interest so apparently that's ok.
Problem is that it's precisely because of the skills, background and involvement with other organisations that raises the possibility of a conflict of interest over certain matters, that they've got the potential to be really good board members or trustees with some highly relevant specialist knowledge.
Like you, I don't know that declaring an interest then not taking part in decisions affected by it is necessarily enough - but I don't think I'd have excluded them as trustees.
I've no idea if they've actually been any good while in post, but on paper they ought to have been.