I’m the same age, and also seem to have heightened hearing at this range. I went to an audiologist for a tinnitus flare up, and did an ultra high frequency hearing test, which confirmed I had abnormally good hearing at 8-16k.

He told me that many audiologists in this specialty believe there is a class of people with sensitive hearing, who are more perceptive to threshold changes in hearing (hence tinnitus). But there’s been no real research on it.

I’m not sure to what extent I believe it (given audiology is somewhere close to physiotherapy in terms of rigour)