No. You do not need joint intent for guarantors as they are not borrowers.
I feel differently, see this section of Reg B regarding the definition of an applicant:
1002.2
(e) Applicant means any person who requests or who has received an extension of credit from a creditor, and includes any person who is or may become contractually liable regarding an extension of credit. For purposes of ยง1002.7(d), the term includes
guarantors, sureties, endorsers, and similar parties.
My understanding is that if you require the owners of a corporation to guarantee a business loan (by policy), then you do not need intent from them. But if you don't require it every single time by policy, or if anyone else who is not related to the business (spouse, etc.) wishes to be liable on the loan (such as for increased guarantor strength), then you must document their intent at application.