Yes, good question, and several people have answered with what my take is on this. The naturally reproduced offspring of the released tuatara are wild but the originally released tuatara are not. The trick is telling them apart, but then that’s exactly analogous to observing a lot of plant species in cities. Sometimes it’s clear that they’ve been planted (not wild), sometimes it’s clear that they grew up from a naturally dispersed seed (wild), and often it’s unclear whether they were planted or not.
In ambiguous situations, I use the observation field “Is it wild?” and set it to “Maybe”. That doesn’t map onto iNaturalist’s captive/cultivated category though, and so I usually also leave it set to wild when this is ambiguous, as it at least then shows up on the default Identify page and can reach “Research Grade”.