Are you saying that "neobanks" do not record the deposits as a liability? Or that they do not record the cash as assets? I don't understand what you are trying to say.
Are there any public "neobanks" you can point to so that we can see the financials as you describe them?
The banking partners have their own bank charter and FDIC insurance, but the technology company itself does not. If you go to most neobank websites, you can scroll to the bottom and see a disclosure along the lines of "Banking services provided by The Bancorp Bank, N.A. or Stride Bank, N.A., Members FDIC".
If you make a deposit into a neobank, you'll have a routing and account number, but the routing number belongs to the partner bank servicing that account. If you deposit cash or a check or whatever, it goes _directly_ to the partner bank.