I took it back to my rebuilder. He worked on it for a half hour and returned it to me. He said there is nothing visibly wrong with the rebuild and on his bench it works fine.
I reinstalled it in my Jetta and it still spun first, then grinded. I was fed up, so I called around to parts stores in the area. One Autozone had a Duralast rebuild nearby. I bought it and installed it just to see if I'm just doing the reinstall wrong. This Duralast fired up no problem.
I'm going to leave the Duralast in for now. I'll return my original starter for another rebuild (he has a 90-day warranty) so he can keep fixing it until he gets it right. I'm hoping this is the last of my electrical issues. New battery, rebuilt alternator, cleaned up cables and grounds, new starter, etc etc... should be good for another 300,000 miles.