Try it yourself and see.. Real easy to test as you only need water, a drop of yeast, some of the syrup and enough volume to fill a test tube for the hydrometer. Which would be approximately 100ml.
If you think about it, it makes sense.. that is not food coloring making D-90 extremely dark brown.
Now, unless you were trying to make something completely unique. Candi Syrup is not often used at higher than 15% of the total fermentables so the impact is not that great in the remaining sweetness.
Your question about flavor still stands, I personally will not make a belgian without using candi syrup as the flavor profile is drastically different than plain old table sugar. If you are wanting something with extreme flavor use D-180, that would show up quite nicely with the black IPA. If you are just wanting ABV, table sugar would work.. my choice would be to use a D-1(least caramelized, aka Simplicity) or D-45.
The great thing about brewing is there are lots of choices and most of the time it leads to good tasting beer.