First-order, yes.

In practice there's a lot of issues with asymmetric information. The company knows its own operations and financial position better than random traders on Wall Street. It is rational for it to buy back stock when the market value is lower than the true intrinsic value of the company, and to sell stock when the market value is higher than the true intrinsic value of the company. Therefore, traders often treat buybacks as a signal that the company is "cheap" (at least in the company's own view) and pump up the price accordingly, and treat stock issuances as a sign that company management believes that the stock is "expensive" and push it down accordingly. Company management has more inside information than market participants do, but is usually prohibited from trading on it. Stock issuances and stock buybacks are one of the few cases where insider-initiated trading is legal, because the benefits accrue to the company as a whole rather than a few individuals.