How frightening for you both, I hope you are both getting over it a bit now.
As for legal Pitbulls, including pure bred dogs, not just those "of the type", everything from drugs to people, and animals, including dogs, are smuggled into this country.
Even prior to the pet passport scheme dogs would be smuggled in, either sedated in cars, or via small boats arriving at unguarded sections of the coast, or up sea fronting rivers, like other contraband, including humans. Not only would this get around the time factor of the 6 month separation quarantine requirements, it would also appeal to some as being much cheaper.
Dogs brought in through questionable means now can be illegal breeds, or legal breeds who haven't properly fulfilled the pet passport requirements.
Illegal breeds such as pure bred Pitbulls will also be brought in with 'correct/legal' pet passports claiming they are cross breeds or other similar but legal breeds (a common defence used in the court cases relating to DDA Section 1 cases).
Not only are not all vets who do the passports breed identification experts by any means, but a young puppy can be near impossible even for an expert to identify as a specific breed when very young. Additionally some vets do not want the aggro of arguing with the owner's say-so of the dog's breed.
Anyone travelling around e.g. Europe, or Southern Ireland, both areas with no shortage of pure bred Pitbulls, even just on a car ferry, will see how easy it would be to smuggle in a dog, unless you were unlucky enough to have a spot check, and an unsuspecting vet could be asked for a "sedative for a long car journey."
Hence there can be, and are, illegal pure-bred Pitbulls in England, many coming from Europe and these will/are also then being illegally bred in this country.
Illegal Pitbulls can be made legal if ordered by the court to be put on the Index of Exempt Dogs (IED). This can either be following their having been found to be Section 1 Pitbull types (including pure bred Pitbulls) and then being granted a contingency destruction order and exemption under Section 4a, if their temperament is deemed appropriate, and assuming all the IED requirements are met.
Alternatively an owner can themselves apply to the court, under Section 4b of the DDA, to have their Pitbull put on the IED, when all the same conditions apply, including temperament assessment, being insured, neutered, microchipped and tattooed, muzzled and held on a lead by a responsible adult when out in public places.
So yes, the DDA was intended to eradicate Pitbull types pure bred and otherwise, and no there are no Pitbulls, or pitbull types being legally walked without a muzzle and leashed. However similarly lawmakers would like drug laws would to eradicate drugs.
However there are illegal pure-bred Pitbulls, smuggled, bred, imported using false breed identification on pet passports etc and these same dogs, if caught or volunteered, may be made legal under the 1996 DDA amendment.
Of course the other loophole can be if a Pitbull owner finds a sympathetic and convincing "expert witness" to declare the dog is not a Pitbull, wins in court, and so has a legal and unrestricted dog, found by the court, possibly erroneously, not to be a Pitbull.