Congrats on your new pittie! Cropping of APBTs tails is not normally done. I hate to ask this, but are you sure it is not a mix of boxer and APBT, or a Boxer? Many Boxers nowadays look like pitties, and vice versa. Boxer/APBT mixes tend to usually have a cropped tail. More than likely, the breeder was an idiot and cropped the tail, or lied about the breed just to get a sale. Regardless of the tail being cropped, it will not harm your dog at all. It will just make reading his intentions and emotions much harder as so much is expressed through the tail (height of tail, depth of wag, speed of wag, etc.). Nubs are hard to read, except that the Boxer has tail movements specifically for the Boxer.
The AKC does not recognize the APBT as a breed, so there is no need for cropping tails or ears. The UKC recognizes the APBT as a breed, and they look at ears only. The AKC does recognize the American Staffordshire Terrier, and the ears are only to be cropped. The tails are to NOT be cropped, as that would be a huge fault.
There are very few dog breeds that actually have cropped tails as the norm.
Papers or not, APBT tails are not cropped. Since the AKC does not recognize the APBT as a breed, more than likely the papers that anyone gets are bogus, which many breeders do to charge a ton of money for their dogs. Any of us can make up “papers”.
Regardless if your little guy has a full tail or not, love him just the same! 🙂