I think the link you cited states that 48 is the median age of infections, whereas the person you're replying to is talking about deaths. I don't have national data, but in my state (Indiana) 51.4% of deaths are 80+ years old according to coronavirus.in.gov

No, that's the median cases age.

what ?

" After exclusions, data for 1,320,488 (94%) cases were analyzed.Median age was 48 years"