I’ve seen some pretty good trees in pretty decent detail. I volunteer at the museum. The trees there, particularly the Japanese trees, mostly have some sort of forward lean. Even the smaller ones.
In working on those I have found the ones that use this technique to be a bit more engaging and balanced to the viewer. I believe the forward bow brings the viewer into the tree and helps balance out the image.
Might be personal taste. I hardly revere traditional bonsai. The majority of my trees are anything but, but I do try to use techniques that work. This one mostly does