I think the entire scene was hyperbole to show just how reckless Kirk and his crew probably were over the last year. To that end, I think it worked marvelously. Think of all the careless, reckless, and not fully thought out things going on (some of which were even called out in the movie). This is where Kirk was relying fully on luck, something that in TWOK, Kirk Prime realized he relied on far too often. In this case, it's still young Kirk probably thinking he's a genius:
-- Enterprise under water. Hey, gotta hide it somewhere. Scotty even thinks it's stupid, which lends some on-screen credibility to it being simply a reckless act by Kirk. Why's the Enterprise under water? There is no good answer,only rationalization. It was stupid, and it was called stupid.
-- Kirk and McCoy's "distraction" of the natives risked the lives of a starship captain and a chief medical officer. Think of how lucky they were that the natives are bad aims or neither of them tripped and fell running through that native grass.
-- Sending Spock down into the volcano. Pike said that was stupid.
-- Sending the shuttle in without extra shielding added to it. They come up with a device to freeze a volcano and a suit to protect Spock, but there's nothing that can add extra protection to a shuttle that's going to hover over an active volcano?
-- The idea that they all willingly take on the mission in the first place. Did anyone think it through? There were no other alternatives?
-- Of course, there's also the problematic nature of the transporter when it would be really useful, which is a Trek storytelling staple and is the reason for all these convoluted events.
I think the point of the entire scene was to show that these were still kids playing with adult things.