Sorta not really
His net worth is reduced but he hasn't actually lost any money unless he _sells_ the stock right now at the suddenly and slightly reduced price. Which would be pretty daft, hypothetically. And the _intention_ of telling people that it's slightly overpriced is for them to sell it. When it's convenient to do so, that is, and not some massive horrible bubble burst. In short; all perfectly fine and frankly more fine than anyone else on the stock market.