UC WCA Telephone Assessment

Just a quick question, do they always ask for a telephone assessment for UCWC? Son in law has severe and chronic disabilities. I am his appointee. Forms filled out thoroughly and evidence provided, but sill they want to to a phone assessment. They also said he has to be present with me but I am speaking for him so why does he need to be there if he’s not going to say anything! Advice please. I’ve gone through this before with my husband and daughters WCA, but my son in law is more severely disabled so I thought they wouldn’t have asked for the phone assessment, but I was wrong!