Since the first dive was successful, there wasn't a good reason to use Musk's submarine. It is risky and scary to use it without any real testing and you don't know if being sealed up in there for 5 hours can give the kids a panic attack. However, it is possible that it would have been higher EV. it also would likely have been a higher temperature whereas the water temp was a huge concern in the rescue. The kids had to wear multiple wet suits.
So, a British diver who helped with the rescue called Musk's submarine a PR stunt that wasn't going to work, saying that it was too big and wasn't flexible enough to navigate narrow passages and corners. Musk responds by referring to him as "pedo guy" in a Tweet that he later deleted.