I’ve never seen a mower quite like that. We have a Perfect brand mower, which has an extension arm that swings like that, but is round, not “y” shaped, with a rubber bumper that slides to assist rolling around the tree, and doesn’t do quite as thorough of a job as the one you shared. It looks like it requires a slow speed to operate effectively, which is expensive, but perhaps it’s worth it. We learned the hard way with our Perfect mower that if you go too fast and don’t give the swing arm time to fully get back into position, it can swing forward and snap young apple trees right off. They’re only 3’ apart from each other in the row.

This is definitely worth considering thanks for sharing!