Yes, the banking credential is just as secure as the government credential. The same authentication process and security requirements are used whether you use your banking credential through Sign-In Partner (Interac sign-in service) or the government-issued credential service called GCKey.
The authentication process does not carry any personally identifiable information such as name or birth date. It relies on strong technology, built using industry best practices. By offering you the choice of using a banking credential, the Government of Canada is leveraging the investments made by financial institutions in secure online environments.