Jo,
Reg B applies to all loans. I’ve looked through the reg and I can’t find anywhere that specifically says that you have to document how the applicant applied for the loan. That being said I did find where it talked about certain things you could do to stay in compliance if the application was taken over the phone.
By denoting how the application was taken this would give your Auditors & Examiners the information they need to decide on what they should be looking for.
I would say they want you to have this for all of your loans. In our loan processing software it is as simple as clicking a box to get this done.