Provided nobody else takes the seat prior to t-72 then at T-72 you should see the block next to you. If it sticks or not is all down to how busy the cabin is, and how many status customer there are. As you are in WT+. the small cabin is usually (but not always) full. If the cabin is full the block will not stick through to checking closing.
Choosing the isle seat with a middle section rather than with a window is a better choice, provided there is not a group of 3 travelling.