Whether a given account for a sole proprietor is a personal account or a business account is really a matter of bank policy and/or agreement of the parties. The accountant in suggesting his client open a business account is really saying "go open an account for your business that is separate from your personal account." The accountant probably doesn't care whether the account is set up as a personal or business account. He just wants the funds separate.
As suggested above, a sole proprietor can use either his/her own SSN or an EIN on bank accounts. The IRS prefers the SSN, since that's how the business's income is reported (on the individual's 1040).
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8