Earlier quoted context omitted.
Buying back stock only creates value for shareholders if the stock is trading for less than its intrinsic value. Above that price buybacks destroy shareholder value. Executives are doing this to meet performance targets and get bonuses. Not to allocate capital efficiently.
Buybacks don't create value. They return the value created by the company to stockholders. They are form of dividends you're just automatically reinvesting it into the company stock instead of getting cash.
Whether the stock is over or undervalued is a bit besides the point, actually. It's a direct flow of cash to investors, that any investor can take advantage if they think the current price is too high (or not, if the price is too low)