Appletree does not HAVE to buy on the bid. The rule states that the buys must take place on the bid or the last published transaction price which could be the ASK. So some of the buying could be Appletree. Also, from the last 4 week Average Daily Volume, they are able to purchase about 60MM shares per day. 25% of 4WADV.
The rules are setup so that a company can execute their buy without undo influence to the market, again paraphrased from SEC rules.
Now if Appletree's broker/MM(and there can be only one handling the transactions per SEC rules) has a buy set at .0003 for 200MM shares for example, it is not uncommon for the price to be walked down to execute that transaction.