Historically, we would say “he HAS a genius”, as opposed to “he IS a genius”, because genius isn’t supposed to be attributed to any individual, when its a gift from God.
If you're referring to actual historical usage rather than how you think people ought to speak, this isn't true. The variants "is a genius", "has a genius", and "has genius" were all about equally common until the middle of the 19th century when "is a genius" started to become the preferred form.
Historically, we would say “he HAS a genius”, as opposed to “he IS a genius”, because genius isn’t supposed to be attributed to any individual, when its a gift from God.
If you're referring to actual historical usage rather than how you think people ought to speak, this isn't true. The variants "is a genius", "has a genius", and "has genius" were all about equally common until the middle of the 19th century when "is a genius" started to become the preferred form.