The presence of the n option attached to the -k5 causes the global -r option to be ignored for that field. You have to specify both n and r at the same level (globally or locally).
sort -t $'\t' -k5,5rn
or
sort -rn -t $'\t' -k5,5
The presence of the n option attached to the -k5 causes the global -r option to be ignored for that field. You have to specify both n and r at the same level (globally or locally).
sort -t $'\t' -k5,5rn
or
sort -rn -t $'\t' -k5,5