User's first access value set to lastmodified rather than actual login time

When a user account is created using bulk upload or manually (I haven't checked other methods), their First access and Last access information appears in their profile as "Never". In the database, these values are set to zero. When the user logs in for the first time, rather than taking that time as the first access time, it seems to use the lastmodified time on the user record instead.

Replication steps:

1. Log in as admin
2. Navigate to Settings > Site admin > Users > Accounts > Add a new user
3. Enter user details and click Update profile - You should be taken to the users list
4. Click on the new user's name to be take to their profile page - Login should be never
5. Wait a few minutes at least
6. In another browser, log in as the new student
7. As admin, refresh the user's profile page

Expected result: The First access and Last access values should be the same

Actual result: The First access time is the time of the account creation (drawn from lastmodified in the DB)