Perhaps I would not call them so, as the customer seems to have no ties to Sutton Bank, I would call them a fintech backed by Sutton Bank. It can be considered being a detail; but see below.
Generally I agree with
@daniels27, adding that what I consider really untrustworthy is the fact that nowhere at the website, even not in the Terms & Conditions, you can find the identification of the legal subject that is doing business as BLUEBANC. Simply, Mr. Nobody is offering you to open an account with him.