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He's also very risk-averse, and she said he refused to even attempt any questions or activities he wasn't 100% sure on.
This may be a sign of developing a fixed mindset rather than a growth mindset. You may wish to read the book Mindset by Carol Dweck. One aspect or application is that gifted kids may stop taking appropriate risks in order to always be "right" or always be "smart" or never be "wrong", and this may work against them. The concept is nicely summarized in these youtube videos:
Ashley Merryman & Po Bronson: The Myth of Praise (link-
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Teaching a Growth Mindset (link-
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You may also wish to read up on perfectionism. A book which seems to understand perfectionism very well and which many find supportive is "What To Do When Good Enough Isn't Good Enough". Another book you might like is "Perfectionism: What's Bad About Being Too Good". While insightful, these are written gently for kids, in a style that is fun and engaging. With any of these books it may be wise for a parent to pre-read and decide if it seems to be a helpful tool to use in guiding their child.