Must graduate applicants who will need funding submit financial statement for I-20?
A financial statement is required by the US for visa eligibility for all international students applying for standard student visas. It is not needed for admissions decisions, as stated in the form you've uploaded.

The purpose of the statement is to show that you will be able to support yourself (and any dependents) while you are in the US. If the university offers funding, you will use that as a source of support on your I-20. If the university funding does not fully meet all your financial requirements, then you will need to show that you can handle the rest of your expenses through other sources.

You don't need to worry about the I-20 until after you've been admitted. The university will give you more information then, including how to submit the necessary documents and what the official program expenses are for visa purposes.