Given what you posted, its unlikely to be backdated to your seperation date. VA is vicious when it comes to enforcing rules as long as those rules benefit Vets.
HOwever, your effective date is the later of the date you applied or the “facts found”, with some exceptions, only ” one” of which you pointed out (when the Vet applies within a year of discharge). Effective dates are complicated, and dont always turn on just ONE thing. There are other things which could result in an earlier effective date.
Example one: Informal claims. If you had a doctor exam, then there are some circumstances when that exam becomes the date of an informal claim.
Example two: 38 CFR 3.156. If you submitted new and material evidence with a “pending claim”, that can becomome your effective date. You should consider taking your file to a NOVA attorney and ask that attorney if there is anything in your file that would warrant an earlier effective date.