Even if you can't provide some information on an application, they usually already have access to most or all of that information once you give them just a few facts so that they can uniquely identify you. And it takes surprisingly sparse facts to identify individuals for this purpose. They do not make you fill out the application for the information on that application per se; their sources of that info are more reliable.

In terms of risk mitigation, they are probably interested in comparing the extensive profile they have of you with what you put on the application. Significant discrepancies would be a reasonable red flag for risk, more so than having incomplete information.