No, they shouldn't be. But I must admit that I lost track about how you want to set devices up. "x2vnc" is for input only. In the scenario I proposed using it, there would be another X server running that is in charge of the input devices, and x2vnc would be used to "forward" these input devices to the other (VNC-frontend) X server. But when there's no such second server running on the RasPi, that wouldn't work.
Unfortunately I'm not aware of a tool that allows to "connect input devices" to a VNC server by other means, so this might be a dead end (for now). The VNC client on the Kindle has no mouse support (yet?).