Dates not returning null

After our upgrade to 10.1.5 I have noticed a change.

Before, in version 9.2, whenever I pulled in the LastVisitedDate from a user profile, if the user has never visited after their account creation (null value in SQL), then it also returned null.

Now running the same scripts, then it returns 1/1/0001 12:00:00 AM.

Is this by design, or is it a bug?