not incredible at all
first, contrary to what most of the public thinks, buy-backs usually have mostly negative implications
it is the opposite of raising capital, and often an admission by management that they have no better use for the money either in their own business, or in any other which they might acquire
second, "insiders" usually includes many, many more individuals than just the board members who approve buy-backs
assuming that the typical insider has better info about future prospects, their selling is merely the result of what they know, and a buy-back in place is confirmation of the negative outlook
on the broader subject of buy-backs, i think they generally operate as a fraud on the typical investor, most of whom think buy-backs are "good"
other than acquiring shares for future use in employee option grants, there is no valid business purpose to buy-backs, they do not change total earnings one iota, in fact, if anything, they may reduce future total earnings as they reduce capital
even the sometimes proffered rationalization that a higher share price is a substitute for dividends and converts ordinary income into capital gains for shareholders is often a chimera as there is no direct relationship between buy-backs and share price
not to mention the fact that to actually receive the income the holder has to sell some small fraction of their shares, something most don't do because a "dividend-substitute" buy-back is going on
The thing that always pissed me off about buybacks is they could pay that money out to the shareholders as dividends. But NOOOO! Can't turn the money over to the company owners. Let company management fritter it away!