Local codes aside;
That is a primary reason for the 'independently supported' language. When a fire occurs above a drop, it may go unnoticed for minutes if not hours. the grid supports become weakened, with additional unanticipated weight it can fail prematurely.
A firefighter crawling below could become entangled in cables, especially around the SBCA.
When pulling a ceiling, the FD doesn't doesn't want spaghetti to fall through when removing tiles.