On its face, the regulation only covers consumer asset accounts established primarily for personal, family or household purposes. [Definition of "account" in §1005.2(b)], and "consumer" is a natural person [§1005.2(e)].
Therefore, commercial or business accounts, including sole proprietorship accounts, are not covered by the regulation.
However, if a bank provides its standard Regulation E disclosures to a business (without a disclaimer of their application to business accounts), the disclosures MAY arguably contractually obligate the bank to comply with the disclosures for a commercial or business account, depending on how the courts of the state in which the account is domiciled apply state law.