There are quite a few extra steps needed for that to work. Just turning that on doesn't let them recover their password.
(Taken from https://support.google.com/a/answer/33382?fl=1&sjid=2812423999389759455-NA)
- "Before you begin: Users need a recovery phone number or email address where they can get recovery instructions"
- "Important: Users who have 2-Step Verification enabled can use only a recovery email address to reset their password."
- "Users who haven't added recovery information are directed to contact an administrator."
So they either need to set their own recovery email, OR, if you have their personal email in an HRM system you might be able to sync this to the directory as a recovery email and let people recover their own password.