I think those transfer rates are typical for spinning HDDs from many years ago. See eg this review of 4 TB drives from when that size was trending: https://www.tomshardware.com/reviews/desktop-hdd.15-st4000dm... - the middle drive of the 2013 comparison has the avg throughput that matches the 120 MB/s max theoretical throughput of 1 G ethernet.

The transfer rates go up roughly hand in hand with capacity.