Someone who has the capacity to be exceptional would probably not be happy to be held back. Would Ramanujan have been happier if he didn't pursue math and became a taxi driver or something instead? I don't think so.
You're creating a false dichotomy. People can be both exceptional and happy. Parents do sometimes create unhappiness by trying to force their children to be exceptional at something the child isn't interested in, but you don't have to do that. You can let the child develop and follow their natural interests and support them without trying to force them to be something they're not.
I doubt anyone is arguing to suppress a child's interest in mathematics but more against trying to squelch their interest in less obviously "worthy" pursuits in favor of making them burnish their college resumes.
The parenting approach advocated for here (freeing people from peer pressure by homeschooling them) is way more likely to produce a 4chan shut in than going to normal schools (which includes Harvard and MIT) is likely to force someone to end up a taxi driver.
However, tutoring your child intensely is obviously important and will result in good outcomes
You're creating a false dichotomy. People can be both exceptional and happy. Parents do sometimes create unhappiness by trying to force their children to be exceptional at something the child isn't interested in, but you don't have to do that. You can let the child develop and follow their natural interests and support them without trying to force them to be something they're not.