I strongly disagree.
If he said, "
Make it...... 100 with a pause, there would be no question, no warning, and no penalty -- he's simply deciding on his bet size amount, no funny business whatsoever (it could have been 80, 200, or all-in). And there's not any funny business with him deciding to stick with just a 40 call amount either, or even a fold: "
Make it..... a fold.", tossing in his cards instead of chips.
The term "Make it..." means nothing, until it's paired with something else that provides clarification.
Only problem here is that "8" failed to provide said clarity.

But his physical action did.