I gave Rowling too little credit (and the filmmakers too much)

Well that solves one mystery. When the filmmakers were trying to figure out a simpler way to give Harry information about Gillyweed for the second task of the Triwizard Tournament, where did they get such a good idea from?

From J.K. herself.

In an earlier post, I had attempted to give the movie guys some credit for coming up with an inventive way for providing Harry this life-saving information: by having Neville learn about Gillyweed from a book given to him by Crouch/Moody and then tell Harry about it.

I thought: that's much better than Rowling's answer, which was to have Dobby provide the information at the last minute. Rowling's approach made Crouch/Moody's gift of the book on herbology to Neville appear to be gratuitous kindness, I argued.

I should have had more faith in J.K. And I should have remembered Crouch/Moody's rant to Harry at the end of the book better.

It turns out that Rowling makes it clear, during that rant, that Crouch/Moody did give Neville the book precisely so that he would tell Harry about Gillyweed. Except his plan was foiled because Harry was too proud to ask his friends, outside of Hermione and Ron, for help.

So, in the novel, Crouch/Moody had to come up with another idea.

The filmmakers shortened the whole process by having Harry finally ask Neville how he could survive for an hour under water. Neville then provides the information and Crouch/Moody's plan was effected.

So this is my mea culpa. I gave the filmmakers too much credit and Rowling too little. I won't make that mistake again.