They do, its just that sometimes it doesn't get executed properly, this is the same when you see pirates swinging a voodoo doll or throwing a pistol in the air. Funny, but not supposed to happen.

It's basically when the Guard draws his weapon while about to continue the animation ( as in he's about to put shovel in dirt/axe in logs ), then drawing the weapon, still weilding the Axe/Shovel. This is my guess...

You cant reason it like that, its just a simple mis communication between the server and your computer, like other people may have noticed, when you see something like this everybody around you doesnt see it.

Yeah, i know that everyone-else-cant-see part. It's the same thing with the sword/doll thing. I like seeing things like that lol.