Just freaking look at it. Do they look like some sagging, yawning, creaking building announcing its demise?
Maybe you haven't heard it yet, but hours before the collapse of WTC7, fire chiefs heard it creaking and yawning, and engineers saw it move and bulge. Femr2 has shown that the roof was moving already minutes before final reelease.
So in the case of WTC7, you are plain wrong: Yes, it was seen sagging, yawning, creaking and thereby announcing its demise.
In the case of the towers, sagging of floors, bowing of columns likewise announnced the coming demise of the buildings, and people heard many loud popping noises ("explosions"), some of which were undoubtedly snapping bolts, welds and other connections.
So if you think that observations of sagging, yawning, creaking, bulging, popping and breaking long before release would be the expected precursors of a natural collapse, then you should conclude that the sagging, yawning, creaking, bulging, popping and breaking that was indeed observed corroborates the obvious conclusion "progressive collapse from fires".