As you lean forward, your sit bones rotate and become closer. That being said, your measurement accuracy and how it relates to the position of those sit bones when you are in a riding position is going to be very dependent on your position when you performed your measurement.

Something you might be interested in -- I believe Specialized dealers have a tool they use to accurately measure your sit bones, and even have a 30-day test ride on any newly purchased saddle. I highly recommend visiting a Specialized dealer if you're unsure.

Some Specialized saddlers are a bit more rounded than others. For example, some measurements may put you on either a 143mm Toupe or a 155 Romin. In either event, you'd honestly have to go there and get measured by their machine to know where you fall on that scale. My specialized dealer loaned me a Toupe while waiting for my Romin Evo to come in.