In looking at the other examples, including mine, the spear is on the left side of the neck in all but your example. This topic has come up in the past, and to be honest, yours is the only example I've seen where it is being thrown in a normal fashion. Of course, like all things, I am most likely wrong. Ask my wife. She was born with a heightened women's intuition. She knows I am wrong even before I say anything. Hrmph!
I really think what we have here are dies that handled the overlap poorly so that the more wear there is, the more it looks like the spear is behind the neck. The exception here is Q's coin which strikes me as oddly styled in the face. Who has a well struck and unworn but normal style coin with rear spear? Bing's coin has the spear going through the neck and is less worn than the fully rear ones.
After seeing coin after coin of Someone Throwing Spear or Slinging Sling in which the spear/sling is passed behind the neck in a manner completely incompatible with deployment of such a weapon, I figured the reason was due to limitations of engraving coupled with a desire to show the thrower from a certain angle. For the spear to pass in front of the figure, the relief of the skinny spear would have to be considerable. There's just not enough depth on a coin to render that in a convincing manner and doing so would create a very thin ridge which would not wear well, and the spear shaft (or sling's thongs) would appear wavy. On Bing's coin and Volodya's coin you can see how the engraver attempted to show the spear passing in front, but the result looks even less realistic because the spear's shaft hugs the contours of the thrower's neck. With the spear passing behind the thrower, at least at a quick glance it looks right. They could have turned the thrower's body, keeping the spear on the "correct" side without having the technical difficult of the skinny relief, but then the thrower would be viewed more from the rear-- less artistic. Just my opinion .
This is always a problem on issues where the spear-thrower is facing right. They could have just had them facing left and then these things wouldn't be bugging us collectors 2000 years on .
They could have also engraved left handed throwers facing right with the same visual result, right ? Q
In product design work, the spear-across-neck relief issue would have been easily resolved with a little creativity: as the spear image passes over the neck, the designer would have slightly sunk the design (making a furrow), instead of making the shaft in relief over the neck. Visually, it would had made a continuous spear shaft and resolved the high-relief problem.