I wouldn't take that as the truth. Sherman only wrote that in the past, Yankees officials have been reluctant to trade big prospects for high salaried players, such as Johan. The Yankees do have an interest in Halladay, but they will not overpay. They need something to get them up to the next level over the Red Sox, but they will not add a ton more salary AND give up the top prospects for Halladay. If the Yankees can somehow find a good medium, then they will be players. If the cost for Halladay is too high, then obviously many teams will drop out, including the Yankees.
If I'm the Yankees though, I'm not worried about saving my pitching prospects in a Halladay deal.