It smells to me like these BaaS companies are a disaster waiting to happen since they do not seem to be regulated in any way. They’re not bank, they’re not part of a bank-holding company, they seem like the ones doing bookkeeping for banks but their books are essentially not audited like a bank’s books would be.
It seems to me like when using a fintech, the ledger for your FDIC-insured deposits should be held at the bank holding these deposits, and at the same time at the fintech itself, not just at an intermediary like Synapse. At the very least, calling the fintech deposits FDIC-insured should come with more stringent record-keeping requirements and supervision.
If the meantime, I’d stay away from any fintech using BaaS companies or FBO accounts.