@PrimeMeridian says ‘if the non-FA student applies ED, and is bound to commit anyway, then what’s the point of dangling a non-need-based incentive?’ That seems to be correct. Colleges prefer ‘free’ students, which mean they don’t need to give away any fin aid. They are businesses, basically.
But does that work if you do not do a FAFSA or CSS? Could a college then doubt if family does indeed have income and assets for full-pay? Or better, say if income is 250K or more, or assets over a million, to do CSS anyway, to prove to college you do have the money to do a full-pay?