Then I disagree with the attorney.
From the OSC 226.5a(b)(6):
5a(b)(6) Balance Computation Method
1. Form of disclosure. In cases where the card issuer uses a balance calculation method that is identified by name in the regulation, the card issuer may only disclose the name of the method in the table. In cases where the card issuer uses a balance computation method that is not identified by name in the regulation, the disclosure in the table should clearly explain the method (emphasis mine) in as much detail as set forth in the descriptions of balance methods in section 226.5a(g). The explanation need not be as detailed as that required for the disclosures under §226.6(a)(3). (See the commentary to §226.5a(g) for guidance on particular methods.)
_________________________
The opinions expressed are mine and they are not to be taken as legal advice.