Thanks for the excerpts from the original. Sadly, it almost reinforces the stereotype of befuddled older people. I couldn't figure it out, either.
SS COLA is based on the CPI-W index. I'd been told at one time that it was typically lower and less volatile than other indices but it does seem to include most of the major items. According to the Motley Fool, it includes Food and Beverage, Housing, Apparel, Transportation, Medical Care, Recreation, Education and Communication and "Other Goods and Services".
Still- I look at inflation in some of those items (Medical Care, especially health insurance premiums, Communication, which would include cable and cell phone bills, recent increases in the price of gas) and they seem to be well above the COLA level.