First and Last names are guessed from Name line when is not needed

I'll try to explain the issue with an example from a faced situation migrating user addresses.

Let's suppose we have this address with below info:
The First Name: John
The Last Name: Doe
The Name Line: Doe John

The issue is that even First and Last names are present, the Name Line field is separated to guess from it first and last names which would result in names reversing:
The First Name: Doe
The Last Name: John

I propose to split and guess First and Last names only when these fields are not present.