<font color="blue"> ...PTO diconnects from the tractor by simply pulling it back. </font>
No, it does not. Neither does an implement drive shaft attach simply by pushing it on.
Look at the PTO output shaft on the back of your tractor. It is splined, but also has a groove ground through the splines around the shaft, more or less midway along it's length. The female connector (on the implement) will have a steel ball/balls that fit in the groove to lock the connector to the PTO output shaft. The ball needs to be "released" for both placing the connector onto the shaft and for removing it. Some connectors have a spring loaded sleeve that needs to be retracted to allow connection/disconnection. My KK tiller has a spring loaded button that serves the same purpose. Other lock/release mechanisms are probably out there.
When connecting a shaft you should make sure the connector has the steel ball seated in the groove. Pulling back on the shaft (as if to remove it) will let you know right away if the connector is properly locked on (ie. it won't budge) . Sometimes, the spring loaded collars/buttons can stick a bit, so you might think it's locked on, but it's not. That's why you give it the "pull test". If you start tractoring, and the implement drive shaft is not properly connected, it will soon disconnect by itself.
OkieG