There are many reasons the boat speed could be higher instantaneously. Momentum from a earlier gust or catching a wave are two I can think of off hand.
Not sure why we are hell bent on trying to prove Jeff_H wrong. Fighting a losing battle in this case.
There are many reasons to love our beautiful old long keeled boats but performance in light airs is not one of them.
Not trying to prove anybody wrong here.
In fact, Jeff is right. Boats are designed to meet the usage the designer had in mind. I only rebutted the "certain model boat bashers" from the standpoint that a boat meeting the designers criteria does not make it an 'all around' poor choice.