That's because there is no such thing as sexual preference (as an immutable characteristic) there is only sexual behavior.
Your statement is the proof that 'homosexuality' is a chosen behavior. How can you tell that one corpse was 'gay' while another one wasn't? You can't.
Homosexuality is a mental disease caused by trauma and is 100 percent curable for those who want to be cured. It is not an orientation or a characteristic.