Is the hiki/tou distinction based on the word or on the object?

So, I do not believe フシギダネ一匹 is at all controversial. It's a small animal, not a big animal.

What I'm wondering is what happens if I were playing one of the Gen 8 games and Dynamaxed him, thus causing him to be half a stadium in size.

Is it ダイマックスフシギダネ一匹 still? Or does it become ダイマックスフシギダネ一頭?