The DLE advise stems from the early DL days, when mounting ears were not all that strong. Because a plane is more flexible than a test stand, DL advised using soft mounting on the test stand. In reality the construction just was too weak, and was changed.
Soft mounting a gasser can lead to more problems than it solves. Think of broken ignition wires, loose ignition caps, stuck carb buttterflies, malfunctioning carb regulating diaphragm.
In chainsaws that is solved by the construction, and carbs are often mounted on a rubber sleeve.