you are both a little incorrect -- shinsoku does technically mean a god-like speed. the shin is "god" and the soku is "speed". but it is not at all godspeed, as in, what you may say to someone setting off on a journey. it doesn't translate that way in japanese. i get the point about godspeed in ENGLISH meaning nothing about speed, but it does still mean a godly speed, so godspeed being used was a misunderstanding of proper english, not japanese. even i shrugged it off at first.
i don't care if shinsoku should mean an extreme speed or the move extremespeed. i don't think any of us has the authority to say which one they mean.