It's always nice to have the flexibility of personally choosing a player. Maybe in one draft u want to specifically pick PG and C since u have an opening in these two respective roles. The order may go as of 'PG'; 'C;, 'SG', however ur first two choices are already picked by someone else, thus left with an SG which u never wanted. This is not really a big change, but it is nice to have for ppl who want to be specific in their draft choices.
.....you do know the "positions" listed there are based on their skillset. so that SG guy you want to manually pass up, could still be a C, or a PG, it'd more depend on how tall he is...