the only reason to use sort and uniq in combination instead of "sort -u" that I can think of is to skip specific columns when looking for unique intances.
example:
...
RH_MEa0001bG06_5 710 14 16 Invalid starting position (14)
RH_MEa0001bG06_4 710 125 12 GGGGGACACCTTCTCTCTCT...
RH_MEa0001bG06_6 710 125 12 GGGGGACACCTTCTCTCTCT...
...
sending a file containing this output to " | sort | uniq -f1" would compare each line and take the first instance that is unique (other than the column you want to skip, column 1 in this case) up to that point and give you :
...
RH_MEa0001bG06_4 710 125 12 GGGGGACACCTTCTCTCTCT...
RH_MEa0001bG06_5 710 14 16 Invalid starting position (14)
...
| 