Yeah, all of this is just my opinion, but I would probably say that's a difference between Auckland and Taronga, given that The Zoo was a beloved, long-running series, and, in contrast, there have been various different series set at (or including) Taronga - The Zoo (2007-2010), Wild Life at the Zoo (2012-2013) and now Taronga: Who's Who at the Zoo (2020-2021), across three different networks. With each new show, the familiarity of animals and keepers is lost somewhat (there's more of them). Generally, every episode has a wildlife hospital storyline, most likely due to the large number of injured wild turtles, kangaroos and so forth which Taronga takes in, and hopefully are then re-released.
From what I've seen of The Zoo, I'd say that your assessment would be broadly correct (and, furthermore, I trust you as you're in much a better position to judge). That's not to say that the vet hospital will necessarily draw big crowds, but it will be interesting to see how it goes. A lot of the animals treated by the Taronga hospital are injured or ill animals from the wild, so there may be some interesting patients in there from time to time.