In theory. In practice, the actual results seldom follow that ideal Inverse Square curve - which applies to light spreading out from a point source with no reflective surfaces. Once you include additional light sources, you now have overlap, and then you add reflective walls... For all PRACTICAL purposes, in a reflective grow tent, Inverse Square Law is seldom useful for predicting overall light levels at various distances.
The REAL trick is to find the distance that gives the most even light coverage while maintaining light levels within the 500 to 1000 Umoles range.