The cord you have is
basically this.
To answer your first question - yes, it is basically an adapter cord so you don't need a dogbone. It is a 50amp female to 30amp male cord.
The prior owner likely had a 30amp outlet at home, or only stayed at places with 30amp pedestals, or as said above chose to buy the cheaper cord since they only had one AC so 50amps wasn't necessary.
To get the use of the full 50amps, all you need to do is get a 50amp m/f cord. If you mostly dry camp then you should be fine using your existing cord. For times with hookups, you should be fine unless you are trying to run multiple high power use appliances like heaters, cooking appliances, hair dryers, etc.