I've also done very similar testing with the same results. Had to redo them several time because iirc at the time nothing had 0 damage volatile emnity or there the moves that sic a pet onto a monster and even now it's only that and other attack commands for pets. Even the huge decrease in emnity that a lot spells got still have at least 1.

Should also note that it was 1 before it was "increased"