I thought that too so I did a little digging.
Seems that “Core Inflation” excludes food and energy. However, the COLA has always been calculated off the Consumer Price Index, which does include food and energy.
For a good explanation see http://inflationdata.com/articles/2008/02/24/what-is-core-inflation-and-why-doesnt-it-include-food-and-energy/
Thank You.