I think it's just something people say to get across how tight the plug was. I've never seen one used to tighten a drain plug.
Standing up underneath a car, where the engine is still hot, and the threads still have oil on them, and you have plenty of room, it is incredibly easy to put a lot of torque on something with even smaller hand tools. A lot of oil changers are also going to err on the side of a little too tight is better than not tight enough. After heat cycling for a few thousand miles, it's going to be a lot harder to take off laying down in the driveway with limited room to put torque on the tools you are using.