noobie question: This form only needs to be included for mailed letters, correct? If delivering through Interfolio my writer wouldn't need to have included this with their letter upload?
I believe that's correct. The AMCAS letter form is used to match the LOR to your application using the AMCAS generated letter ID. If the letter is submitted through Interfolio, there's a place to input the letter ID if I remember correctly so I believe the AMCAS letter form is not necessary.