When I say "artificial" what is mean is that if for example a turn-around CEO and/or team is compensated partly or largely in stock options then they can decide the best way to raise the stock price is not to grow sales and profits but to spend the company's cash reserves on a buyback.
Other investors are often supportive of this as it gives them a profitable exit from the soon to rise stock.
On its own, less supply leading to higher prices is perfectly natural.