Gap-fill in general is very useful for not just palm trees but other stuff. Also in studio u can almost replicate everything made in blender with unions. I have done unions for a long time now and I can say that using unions to create complex creations is better then using gap-fill cause the biggest issue about gap-fill is it creates a lot of parts and you also have to make sure the bottom part of the filled area was filled properly cause you select sides to fill not surfaces.