Okay okay so first of all, there was no need to post it three times.
Then, nowhere it says a Halberd has to be as tall as the one who's wielding it. Sources usually give us a length 1.5-1.8 meters (which is btw. even shorter than many people are). Of course with some exceptions as always.
An axe, as you claim it is, is about the length of the arm for battle purposes. The shaft alone of here is longer than their arms.
Last but not least, the Halberds (yes they are) the four-armed guys are wielding ARE about as tall as they are (the line is copy pasted and just moved from the Halberd to the body. It's the exact same length):
And as I've already said before, the halberd doesn't even have to have the same proportional length for these guys. As long as they can fight opponents without the opponents being able to reach them it's doing its job as halberd.