That doesn’t sound right. How can you guarantee zero fly/fruit fly eggs in something like orange juice with pulp. Fly eggs are tiny and can be found on fresh fruit skins even on the trees. Certain juices preclude the kind of filtration that could be used to achieve 100% fruit fly egg removal. I don’t know anything about European food regulations, but from a practical perspective it seems impossible to guarantee ZERO fruit fly egg contamination. Especially considering Europe tends to be more flexible with insects in food than the US such as Casu martzu.
I suspect if there really is no max insect parts limit, there is a procedural requirement that ensures contamination is kept low.