In general, Medium Blue Fluorescence is a detraction in a Fancy Yellow Diamond.
I'd say that in 70% of FY/MB stones I've seen over the years, the color was negatively affected by the fluorescence. In some cases minor, other cases really bad. So, based on my experience, the reputation is earned. Especially in online sales.
In about 20% of cases, it's neutral - the fluorescence has no impact on color, on way or the other.
That last 10%? Stones, like this one, that benefit from the fluorescence. One explanation is that GIA is tougher on fluorescence yellow diamonds.
With this much color and no fluorescence, the stone would have gotten Fancy Intense Yellow.
The color of this stone is amazing. The cut, as well.
Nice crown- nice spread- lovely organic shape. No bow tie whatsoever I love a great looking pear shape, of which this a great example.