See the commentary to 1002.10. It appears that they can, but elected not to. Reporting is mandatory for spousal joint applicants.
Official Interpretations of this section.
Section 1002.10—Furnishing of Credit Information
1. Scope. The requirements of §1002.10 for designating and reporting credit information apply only to consumer credit transactions. Moreover, they apply only to creditors that opt to furnish credit information to credit bureaus or to other creditors; there is no requirement that a creditor furnish credit information on its accounts.
2. Reporting on all accounts. The requirements of §1002.10 apply only to accounts held or used by spouses. However, a creditor has the option to designate all joint accounts (or all accounts with an authorized user) to reflect the participation of both parties, whether or not the accounts are held by persons married to each other.
3. Designating accounts. In designating accounts and reporting credit information, a creditor need not distinguish between accounts on which the spouse is an authorized user and accounts on which the spouse is a contractually liable party.
4. File and index systems. The regulation does not require the creation or maintenance of separate files in the name of each participant on a joint or user account, or require any other particular system of recordkeeping or indexing. It requires only that a creditor be able to report information in the name of each spouse on accounts covered by §1002.10. Thus, if a creditor receives a credit inquiry about the wife, it should be able to locate her credit file without asking the husband's name.
Integrity. With it, nothing else matters. Without it, nothing else matters.