Paul, years ago some of the small speed light makers (Vivitar 283/285?) had some yellowish filter over their speed lights. I don't see that with any of the new ones so I guess they think the digital cameras will compensate for the WB automatically.
However, I suspect they are missing out the fact that using them with daylight causes a blue tint against the warmer sunlight. My Nikon SB-900 measured out to be around 6,500K which seems really blue and cold in use, besides well outside what Nikon's default flash WB is too.
Nikon seems to call Daylight 5,200K in their settings. If the Einstein is 5,650K, would adding something for a 20+ Mired shift (Lee #444 Eighth C.T. Straw) help if one keeps the Nikon set to Daylight for outdoor flash fill and not Flash which might be 5,600K?