I may be confused here but didn't the e2fsprogs come with (or used
to come with) a test program called expand (or extend) that added a
block group to an existing ext2 fs?
No, there was never such a program with e2fsprogs. I'm currently
working on a program that will allow you to resize ext2 filesystems, but
it has a ways to go before it will be ready to be released.
- Ted