So we looked into this and turns out Use of Representative (IMM 5476) is correct, and the language clearly says a representative could be a friend, family member, immigration consultant or lawyer. The reason they asked us to do this was, spousal sponsorship application is always linked to the primary applicant, which isn't me. They need to validate all information through my spouse and no one else, unless my spouse gives me the authority to do so. When you go to IMM 5476 you'll see the option to select the relationship of the representative with the principal applicant, one of which is spouse.
So basically this
is the correct form to fill.
Here's the link for
IMM 5476 and the
Web Form.
Our workaround to avoid this extra documentation is for my spouse (the principal applicant) to call them directly.