I think that the definition of Initial Fork Offering is pure marketing. An Offering requires that someone offers something so that someone else can accept the offer. In a fork, there is no offer. Before the fork, you have 1 X, after the fork you have 1 X and 1 Y. You didn’t accept any offer; you just had them.
Btw, it is curious that the acronym is the same I used for Initial Free Offering in my post at https://medium.com/0xnil/initial-free-offerings-as-an-alternative-to-icos-cfb318505566.