They seem like they also directly attempted to measure actual PFAS, but then mixed the results with fluorine, I could not quite understand what they did. Maybe someone can interpert?
I don't like using organic fluorine as a proxy for PFAS, because fluorine also exists naturally in the environment - we mine it from the environment after all.
The paper uses box plots (https://news.ycombinator.com/item?id=40765183), on a log scale even, so it is hard to estimate the actual frequency of PFAS within the samples, but from Fig. 4 it seems like PFOS (51 ug/kg) and PFNA (68 ug/kg) were the most prevalent PFAS chemicals. For California the limit for PFOS is 0.15 µg/kg/day which for a 200lb person translates to 0.26 kg liver/kidney or about 9 oz. The FDA's serving size for liver is 3oz. So yes, it is high, and of course there are other sources of PFAS than food, but it doesn't even seem particularly problematic, unless you make a habit of eating wild boar. The EU's standard is based on within-food measurements, and is 50 ug/kg wet weight. The headline is wrong, 230 ug/kg is dry weight but wet weight is naturally lower as the denominator includes the water - it is more like 1.36x. Although I guess the sum of PFAS chemicals concentrations (median doesn't appear in study) might add up to around 3x-4x.