What if all the scouts collectively agree drafting the positional need is more likely to provide value than drafting the guy they have one spot up?
The point is you are trying to achieve a goal, and sometimes that means considering all the factors that go into it. When the difference between the next guy up and the other that get tighter and tighter, those other variables become more likely to push the needle to the other side,
Just like a team might trade an objectively slightly better player to fill a positional need, you can choose to draft a guy that better fills a need. Just as an extreme example, say you have a full sleight of goalies in the system, two guys at every level, all young enough that theyll be around for a while yet, and next up on your list in the 6th round is a double overage goalie, with no roster spot available, an a D that could fill a roster spot in the AHL on a couple years as the guy one spot back on your list, do you draft the guy that you won't have a roster spot to play next year, or the guy ranked one spot later?
In the real world, teams make these decisions all the time, they weigh all the factors rather than ignore some just so they can say BPA even at the point where BPA becomes less and less meaningful.