A lot of confusion comes from the term “hard-wired”. The term hard-wired means the cable comes furnished with the product and is physically connected or hardwired into the household wiring. There is no plug to plug in.
All built-in appliances such as; built-in ovens, have conduit with the electrical leads attached to the range. They can then be connected right into the household wiring.
When a pond pump is wired directly into an electrical box and we can use a switch to turn it off or on. If we do not hard wire a pump, we can simply unplug it to turn it off/on. (Hard-wiring may void the warranties of some pumps. Check with manufacturer before hardwiring.)