I believe tha this story is true, I think dolphins helped Nikki to speak, my theory is the next:
I think, when you are lack of security, and something or someone change this,an dyou feel better with yoursef you are capable to do all the things that you want, when Nikki was rounded with dolphins and he saw how they are capables to communicate between them, he understood he could do it with words.
I think Nikki's mother raised that money in different therapies to help her son, and medics in EEUU are more expensives than in Europe.
But when someone of your family feel bad and nobody know what is hapen you don't maind spend your money in a lot of medics,if someone is capable to found a solution.