How many homosexuals have refrained from sex with other men for the last week let alone the last year? I would say all of them. Next, how many with disease from sexual relations would be symptom free for 1 year?
Keep in mind the “ever have sex” question was self reported also. The blood screening questions always have been based on self reporting.
Outward symptoms of undiagnosed HIV take multiple years to show, and also the screening process is not perfect. I am not sure what they are going to tell you now, but last year when I tried to donate blood, but can’t because my blood pressure is chronically too high, that you should NEVER use donating blood as a diagnostic to screen yourself for blood borne diseases, because the screening can read a false negative.