FlyingEgghead

After further clarification of what EXPLAT meant, the answer is: Apparently no one previously in F had specifically wanted those seats, but these 4 pax did. The intended meaning wasn't that anyone in F would obviously prefer row 1; it was that (per EXPLAT's observations) the 4 upgraded pax near-simultaneously changed their seats from their "scattered" initial assignments in F, which is enough to conclude that those initial assignments were not chosen deliberately by those pax (why deliberately choose scattered seats only then to promptly change to adjacent ones?). In other words, it's the fact that the pax had to actively change their seats, not the fact that they changed to any particular row. This is how EXPLAT concluded that the F seats resulted from system-generated assignments in an auto-upgrade.