Looking at the ashell sources on the 1BSD tuhs utree viewer suggests that ~ wasn't there yet, but that it was planned:
* Changes to glob to allow ~, prevent too long path, and prevent
* perhaps running out of directories.
...
Looking at glob.c, there's no ~ nor 126/176/7e in the sources. Editing the cont.a archive directly confirms no ~ or similar constant is present.
By 2BSD, it was in sh.glob.c in the 'expand' function. Later versions define TILDE as '~' and used that. V7 had no ~ in the shell, but as you point out uucp there supported ~ for user home directories. V6 didn't have any of this included that I can find.
Warner