The Nashtah Pup being a Z-95 was invented for X-Wing Miniatures. Tales of the Bounty Hunters described it as something very different (a 2-man mini-shuttle with hull-mounted ports for a pair of lasers, which when detached had room for a pair of dead Wookiees to be stuffed inside), and the deck plan Kael linked to shows a wingless shuttle that's a far better fit for that description.
Presumably FFG was just trying to incorporate some of the Hound's Tooth's Legends fluff into the game without needing to turn that tiny little picture into an actual ship.