I think in the old days,
You had to read through the back chapters, to see if additional fire extinguishers were required, for whatever reason.
So someone decided to add the chart, so it tells you in one place, more are required
Ok in looking at a few referenced sections, it does just send you back to 906, like you say.
Well guess they needed to add a few pages to an edition???
I guess check the table, because some do require do require extra extinguishers
Have to live code speak