If you recall the discussion in Fluxes for soldering, you will remember that there is a relationship between the wetting time and degree of flux activity. From that, you would expect all the points showing the wetting of the component to move to the right, and for the left-hand side of the process window to shift in the same direction.
Typically, because joints which take time to wet fully frequently have a higher intermetallic content, and more inclusions of oxide, dewetting can be induced to happen faster than when good wetting has taken place. Whilst this result is based on an understanding of the mechanisms involved, rather than actual measurement, one would expect the right-hand side of the process window also to move inwards.
In other words, using a flux with insufficient activity reduces the width of the process window, and may even eliminate it. Flux activity has to be sufficient to enable fast wetting of the surfaces to be soldered.