Based on recommendations from Betterment, Betterment Cash Reserve accounts are grouped under the Investment accounts section. Betterment has confirmed this as the account type and as such we are unable to change the designation.
Since Betterment is not a bank and does not have a routing and account number, we cannot consider it a bank account. While these accounts may be primarily cash accounts, they can be used for trading and are not traditional 'bank' accounts.