A convenient reality as they can also just be used to constrict the supply of shares on market more and more, which is what they do. How also convenient that it can result in gains much more amplified than dividends.

Yes, your observation is also true. But lets not pretend companies were really trying to choose between dividends and buybacks, most don't do dividends and ultimately never return capital to shareholders, which is the point of stock: to act as a conduit in sharing earnings.