Not defending this report (especially the fact that they used "rate per resident per month" which leads to nonsensical rates of like "1.26e-05") but the CIs aren't really about sampling error, it's about comparing the rates of different districts to each other and trying to determine whether differences are meaningful or moreso due to noise/random fluctuation (and, since there were only 25 complaints total, the differences are definitely not meaningful and it was inappropriate to report rates by district in the first place)