The prime window for reshaping a roster starts the week before the draft and ends around 7/15 (my birthday is 7/9, hence the comment about my birthday).
Yet last year, when I said that I didn't expect much to happen after the Clifton and EJ signings happened that first week of UFA, I had so many people telling me that I was being too pessimistic and big moves could still happen.
And we all saw how that played out...
Everyone who hangs onto the possibility of a move points to the Skinner trade which was one of the few outliers that happen in August as the reason why is so much grasping at straws.
Rosters are built Draft Week. If things aren't done then, it likely isn't happening because teams will have their cap allocated and roster positions filled by the time Dev Camps start.