Regular consumption of these mushrooms leading to an additional 0.27 mSv doesn't concern me even a little.
All publications and news discussing radioactive contamination should be required to be quantitative in mSv units like this one. The difference between detectible and hazardous in radiation is about 10 orders of magnitude.
https://www.epa.gov/radiation/radiation-sources-and-doses#av...
More dose info; https://www.energy.gov/sites/prod/files/2018/01/f46/doe-ioni...
But it is interesting to note that the relevant consumer laws prevent the sale of eg. derived wild boar products from affected animals with similar contamination, which must be doing wonders for the French wild boar meat trade.
Aircrew have higher risk for certain types of cancers, but it's not clear if radiation plays a role in that. And of course they spend way more time on air than any regular airline customer.
E.g. getting hit by radiation briefly from the outside is different than having a radiation source inside your body for potentially ever (heavy metals are known to do this).
I am not sure how it is with mushrooms, but as someone who grew up in the Austrian South with similar laws regulating mushrooms I think this was the reasoning. So not that the radiation dose of one of those mushrooms would be problematic, but that it contains radiating particles that happily enter, but not so happily exit your body.