Maybe the emphasize is on the little word "all" in "he was claiming all the questions", at least thats what Í guess. If so, then I see the problem is not GM specific but is more appearant when a GM is doing it.
Also a player can claim all the questions, simply by typing faster/having less lag. When I started advising, there was a player also claiming all the questions and also answering all correctly. Back then I didn't know about claiming, and also would have taken more time to answer than him, but nevertheless I was a bit disturbed as he didn't leave others any chance to answer even simple questions. That's when I /told him nicely that I like to answer simple questions and he didn't make a hassle about it.
I think as good advisor one shouldn't claim easy questions (or claim after a little while, giving others the chance to claim), to give other people, whether beginner or not, the chance to be helpful (even if it sounds weird).
However, I don't feel that can or should be solved via rules or game mechanics. One can look at it as little practice of common sense.