The pieces of foam breaking off increased when the contractor (Lockheed Martin) changed to a government mandated "ozone friendly" compounds. This happened everywhere in the aerospace industry, and other industries. The government simply baned substances that leached Volatile Organic Compounds into the atmosphere as they dried. (Thus, you can't buy the kind of paint you used to be able to buy.) The new compounds allowable were not as good as the old coumpounds. (For example, MEK was outlawed, and it was the best cleaner-degreaser known. Ethanol alcohol was substituted, but does not leave surfaces as clean.) Less clean, means more stuff not stuck as well. The process changes were so widespread that engineers could not test them all well enough before the shuttle had to sly again, but the new processes were "certified" anyway.
The company had the option of petitioning the EPA for the old process if a new one could not be found that was good enough, but contractors like Lockheed, long a target of environmentalists decided to make a political gain by accepting all the changes and agreeing not to put out any challenges. Thus the shuttle foam process was changed and more debris were deemed acceptable.
I believe what NASA is trying to say is that the new compounds were just as good, but the process of application by hand does not yield repeatable results. This was my experience in working with hand mixed compounds as well.
Thanks for the illumination. :))