It is a signal. That is the only possible logical conclusion. Indulge me for a minute...
If someone was a CEO who owns 1,006,625 shares. He decides to increase his position. Would it make any kind of sense to buy 375 shares at a time? That is comparable to someone who owns 10,000 shares making purchases of 3 shares at a time.
Not only is that ridiculous and meaningless, but it is also a hassle since he would have to file with the SEC every time he makes one of these tiny buys. Why not just make one larger purchase?
I say the only logical reason for all of the effort is so that it draws attention to the purchases.
Now... if he's obviously trying to draw attention to the purchases, the big question is: WHAT IS HIS MESSAGE? Not is there a message... but WHAT is the message?
I'd say that a "buy" can only mean a signal that it is time to buy. If he was trying to send a message about bad news... or trying to give hints that you should sell, I'd expect any logical person to "sell" as a signal.