It's a balance between pure BPA and drafting for need. The goal is to fill the needs during free agency so you can pick BPA to upgrade some of those positions.
For example, we have at least a "serviceable" starter at every position, so Beane looks at the roster, figures out which positions would be nice to upgrade, and moves around (if necessary) to align the BPA at those positions. We have decent receivers, but other than Diggs, nobody elite, so that's a spot that's ripe for an upgrade. It looks like Kinkaid is more of a receiving threat than a blocker, he was the best pass-catcher on the board at 25, and Beane figured Dallas was going to grab him at 26, so he moved up and got him. BPA at a position that would be nice to upgrade.
We could also use upgrades at MLB and OL, so I expect to see those positions addressed today and tomorrow.