I don't see it as being unreasonable. It sounds like your DS's asynchronous skills - lagging behind in art - are hitting a raw nerve with you, because of your profession. That's perfectly reasonable.
Your DS's fine motor skills may lag compared with his peers because he grade-skipped. I'll bet he will catch up. Growth in any area is not necessarily linear, and he may surprise you in the next few months/years.
If it's really vitally important that he learn certain art skills, why not offer a small incentive? My children will attest - I'm not above bribing if the stakes are high.
