Not to get too nerdy but the island at IOA is not Nublar, (or at least wasn't when it opened.) The island is named
Isla Aventura and in-story this island is near Orlando, FL. The queue video and the model at the ride entrance go into it in a little more detail. Small changes like the Visitor Center being named Discovery Center also hint that this is a different place.
Following from
Wikia:
Jurassic Park: Orlando is dinosaur zoological/theme park located on Isla Aventura, an island near Orlando, Florida. It is described as "the park that John Hammond would have created, given to have an opportunity to have a second chance." The first animals representing 16 species in the park were transported from Site B to Orlando. The park opened in 1999.
The Jurassic Park themed attractions of the Islands of Adventure are meant to be located on this island. In interviews and talks the park staff will pretend like the dinosaurs are real and that they work for this fictional park
Technically speaking, the film-makers intended the Jurassic Park rides to be the "Happy-ending" for Hammond and InGen, though this isn't actually canon. The story is, after Hammond's failed Costa Rican park, Universal allowed him to build a new Jurassic Park on an Island in Orlando near Universal Studios. Steven Spielberg and the ride-developers even went as far as getting Richard Attenborough to reprise his role of John Hammond at the Visitor Center (or Jurassic Park Discovery Center) for an introduction video before the ride.
All that aside, I'm not sure it really matters in-story if they build a coaster here or not, because at the end of the day Jurassic Park is a theme park after all. Heck, Jurassic World in the film has a water park behind the petting zoo, so really anything's fair game if you ask me.