We don't have any "issue", this is instead a good and proper OPTIMIZATION feature.
Those other sceneries you are citing appear to "work", but with an obvious heavy cost in fps, especially when used in combination with airplanes using DL lights, just because they just place the DL effects, without doing any optimizations.
Instead, what you are seeing, is the result of our software optimization, that defines specific areas, like virtual polygons, which activates ONLY the lights closer to your airplane, sometimes as precisely as enabling them only on the same SIDE of the terminal your airplane is on (so it's far more precise than "just" a range check, which is circular/spherical, instead of a carefully programmed polygonal shape).
So, instead of having all the lights enabled at the same time, which could be several dozens, we are always sure that not more than 5-6 of them are enabled at any given time, which are usually the ones close to your airplane and your own AI.
So, our sceneries don't show the big drop in fps normally associated by using an airport with DL AND a complex airplane with DL as well, and it will also not drop too much, when you'll call GSX vehicles with their own DL effects.
The general rule is: whenever you see something "different" in FSDT, compared to other developers sceneries, instead of assuming it's an issue, ask yourself "maybe they did it on purpose, to get better fps ? ", and you find the answer, most of the times, it's yes, since we firmly believe there are only 3 things that matters in a scenery, and it's FPS, FPS and FPS...