I've been researching this as well. Here's a 1964 Chrysler video that explains some of this. It appears they use sealer when putting back in the glass. Look at the 13:00 minute mark.
Here's another video from 1975 that goes more into depth about sealing the windshield:
[ame="https://www.youtube.com/watch?v=xa-i_u0v34I"]https://www.youtube.com/watch?v=xa-i_u0v34I[/ame]