JWE Spinosaurus should not be 14-15 meters long because this is a wild wild estimation of the real world Spinosaurus, which have nothing in common with the movie one.
JP3 Spinosaurus is 13 meters long, maybe less, but certainly not more. And that's what the JWE one should be based on.
Okay - this where we are going to disagree, a bit .
Yes - the official JP3 stats for the Spinosaurus lists it at - 13.3 meters/43.75 feet long. And Yes - the JP3 Spinosaurus - is a very different dinosaur from the modern real world Spinosaurus. However there is no indication - that the JP3 Spinosaurus was fully grown.
The best estimates for Spinosaurus length based on the current skeletal model is at least 14.9-15.24 meters/49-50 feet long. But keep in mind this is semi-quadrupedal Spinosaurus . The older bipedal model of Spinosaurus is more like the JP3 Spinosaurus - however even those estimates suggested Spinosaurus was at least 14-14.6 meters/46-48 feet in length.
Honestly - the length estimates for these carnivorous dinosaurs - I would prefer to see is the following
Tyrannosaurus rex - 12.8 meters/42 feet long, 5 meters/16.4 feet tall, and a weight of 8-9 metric tons - - - This would be a good average for the adult T.rexes of the Jurassic Park/Jurassic World Series.
Giganotosaurus - 13.1-13.4 meters/43-44 feet long, 4.6 meters/15 feet tall. and a weight of 8-8.5 metric tons
Spinosaurus - 14-14.3 meters/46-47 feet long, 6.1 meters/20 feet tall(at top of spines) and a weight of 10-11 metric tons
Indominus rex - 15.24 meters/50 feet long, 5.8 meters/19 feet tall, and a weight of 12 metric tons.
As these figures are the most realistic, yet they also fit rather nice in to Jurassic Park/Jurassic World canon,