url=https://ocv.me/stuff/rips/enc/realjaycorehours-2019-0928-h265-vslow-crf36.mkv

ffmpeg -i $url -map 0:a -c:a pcm_u8 -sample_rate 22050 -t 80 tmp.wav
# works as intended, grabs the first 80 sec

ffmpeg -ss 0 -i $url -map 0:a -c:a pcm_u8 -sample_rate 22050 -t 80 tmp.wav
# gives 34 sec output due to adding -ss 0
# but metadata indicates duration 1:19 when writing to nut instead

ffprobe -show_packets -select_streams a $url | grep dts_time | less
# dts/pts looks fine

guessing that -ss always targets video? can you make it do audio instead?
adding -vn as an argument before the -i does not help,
putting the -ss after -i DOES work as intended