In an AR headset the final desired design is overlayed within the hedge, and you trim the parts outside. Now try to imagine how you might accomplish something similar without an AR headset. It would be very difficult.
That said I'm sure there are experts at those methods who would leap at the chance to model their work in more forgiving methods, digital or physical, and use that kind of technology to guide them as they carve!
The method I described with an AR headset makes it something that anyone could do with extremely minimal training.
AR could still help - if an app could visually inspect the surface of your material, or the branches of a hedge, it might be able to flag warning signs.
But for any other material it would be helpful.