I did a split comparison in gimp and the stock reflection is almost the same as the milky white reflection. It's almost as though the reflection being generated is using the original colour of the sea, the light blue colour. It's actually more or less the same colour as the reflections in stock, it just looks lighter because of the contrast between the darker sea.
Here's akdavis' screenshots, with the first one placed side by side:
The reflection seems to be the same colour, but looks smoother as the water doesn't have any dark bands in it.