I am not sure what to make of this modification. There is an article from Reuters that says it is being carried out to improve reliability/effectiveness of the fire suppression system in the electrical equipment bay which just happens to be the location of those batteries.
What puzzles me about it is the use of Halon as the fire suppressor. I thought the manufacture and use of Halon had been banned decades ago?
U.S. proposes plugging fire-suppression hole in Boeing 787 | Reuters