It’s a bad solution anyway since the result you get is not instanced.
You need to make your spline system smart enough to pop in instances instead of mesh parts whenever possible.
Its likely best to leave the spline alone entierly, place individual mesh instances along it manually, wherever possible, and use the spline to spawn custom curved connections where you can’t.
If you do that, then the various curves will already be individualized (between straight instancsd pieces) so exporting the resulting mesh in blender and using “split by loose parts” will generate all the separate meshs you need with the proper “drag and drop in engine” position offset that they require…