In DX9 the effect works perfect. Since the product states it is DX10 compatible, I have not converted the particle effects to DX10 with the fixer.
GSX is compatible with DX10, meaning that it works with it but, of course, if there are still bugs in FSX, there's not much we can do to fix it, that's why the DX10 Fixer exists in the first place: not just to fix addons which are not DX10 compatible (GSX is), but to fix problems in the DirectX 10 mode in the sim itself.
And, not only the effect works in DX9, as you have noticed, but it works also in P3D, which runs under DX11 so, clearly, the effect itself is correct and compatible with every DirectX version, provided the sim doesn't have bugs.