No, it is broader than that; it is not limited to bank notes or durations less than 9 months, but to any bank-issued security; but since Coinbase is not a bank as defined in the Securities Exchange Act [0], the bank-issued securities exception is immaterial.
[0] to wit, per 15 USC § 77c(a)(2): «any national bank, or banking institution organized under the laws of any State, territory, or the District of Columbia, the business of which is substantially confined to banking and is supervised by the State or territorial banking commission or similar official; except that in the case of a common trust fund or similar fund, or a collective trust fund, the term “bank” has the same meaning as in the Investment Company Act of 1940 [15 U.S.C. 80a–1 et seq.]»
It is not required for it to be issued by a bank for it to be exempt.
Even if you are right that tradability is not a requirement of a security, and even if you are right that this meets all of the requirements of a security, I still don't see how the SEC has jurisdiction here. The Securities Exchange Act explicitly exempts bank notes with duration of less than 9 months from SEC regulation. Interest bearing bank accounts have the unique feature that they have no required investment term: you can deposit for a century, or you could deposit for a millisecond...the interest is paid for the duration of the deposit, and the duration is entirely determined by the depositor, and is not a term in the contract. The SEC admits that even short term CD's (undoubtedly an investment contract that passes the Howey Test for a security) do not meet its legal bar for jurisdiction, so why they would try to apply it to a unrestricted withdrawable account (regardless of the underlying asset class) is absurd to me.