Why would seats open up on the seatmap?

I'm flying UA44 on Saturday and am waitlisted with a GPU. The BF fare buckets are J0, JN0, C0, D0, Z0, ZN0, P0, PN0, R0, RN0, IN0, I0 and have been for a week. Until last night the seatmap was showing no BF seats available, but suddenly overnight 3 seats are showing as unassigned.

Any idea if I can read anything into this?

I'm considering SDCing to an indirect (probably via ORD) flight overnight Friday to get the upgrade to C, but would rather not if I think I have a decent shot of clearing at the gate.

Edit And they've gone away again!