Hill provides some new detail. Going into the draft, Dallas had three primary targets they were hoping to get at 18, which match up with what many fans were saying: Guards Chance Warmack and
Jonathan Cooper, and safety
Kenny Vaccaro. Further, Jerry Jones was committed to upgrading the offensive line or safety at that draft position, or trading back. Defensive line was simply not part of Jones' thinking.
The scouts wanted to go pure BPA, and felt the high grade they had on Floyd (quoted here as "top 10", which would not conflict with the # 7 position cited elsewhere) more than justified taking him. And according to this account, the coaches had a similar viewpoint to Jerry, so the split was actually more down the middle of the war room. And the scouts got outvoted.
They didn't expect Floyd to be there (at 18), so there was a long discussion on Floyd. Jones sided with the coaches.
That puts things in a bit of a different light. Since the article specifically says "coaches", it would certainly indicate that Monte Kiffin and Rod Marinelli had input.
It is possible (just to speculate) that Garrett was inclined to go with the scouts, but Kiffin and Marinelli were in step with Jerry. But regardless where each individual stood, the information presented by Hill is that the scouts wanted Floyd because he was so high on the board, the coaches were not sold on his fit in Kiffin's 4-3 (possibly because of his low sack total in college since Kiffin is all about pressure on the quarterback all the time), and Jones did not want anyone except offensive line or safeties. With no players fitting Jones' desired profile, the trade option was selected. The scouts lost out in a three way disagreement where they got outnumbered, and they felt that the team erred in deviating from the board at that point.