GWSes are analog. But good thinking. I just tried 2 GWS servos, and it doesn't matter if
the signal pin is grounded or not. One of the GWSes simply twitches noticeably on power
application, and then comes back to the same position. The other one turns 20-30 degrees
or so, even with a moderate torque load on it.
I got a new servo yesterday, and it does the same thing. It does twitch in the opposite direction though.
I'm adding a relay to delay the power to the servo.
When you start up an Arduino, the servo will automatically jump the servo a bit and move. One way to prevent this could be to always have a voltage applied, but maybe like a "sleep" mode where no power is being drawn other than the LED on the main board. Does that help at all?