I agree the term does not apply to 2,4 D, but this sentence shows the actual chemical genres reviewed:
“The 19 candidate pesticides not previously linked to prostate cancer included 10 herbicides, several fungicides and insecticides, and a soil fumigant.”
They are using a strange definition.
Without delving into all the details, this study seems odd. They’re finding an association many years later, to exposure to one broad class of chemicals, pesticides and herbicides.
Wouldn’t the subjects have had environmental exposure to many other things over all those years?