I just tried it out. When I first posted I didn't have a function generator, so I figured I could get easy answer online, but now I do and with PWM output to bat. It worked. I supplied 5V to the power leads and then applied the 3.3V as the PWM. I got it down to 2.5V before the servo went jittery. Also, fyi, you all might have known this but I found that ramping that 5V power supply keeps the servo from jumping initially as opposed to an immediate 5V supply that always makes the servo jump.
This leads me to another question. If ramping is not a possibility can one supply the PWM first before turning on the power to try to keep it from jumping? Will that mess up the servo? How do commercial servo controllers do it? They never seem to jump (other than jumping into place).