In the past (early 2000s) they used to automatically block the seat next to any Gold or Platinum passenger.

When all the other seats were all full, these blocks would be removed, but most of the time it worked out great.

My wife (gold at the time) would choose the aisle seat and I (Plat) would select the window, which would result in the middle seat being double blocked. Most of the time we would get the whole row of three seats.

-Mike