Table contains the range of overlap coefficients for each system separately as well as the overall dataset using different durations of the fast alchemical transition -400 ps, 600 ps (our standard protocol), 800 ps, 1 ns and 2 ns. It also includes the number of complexes with zero overlap for each case. Strikingly, the number of complexes with zero overlap between the two work distributions are 125 (57.08%), 108 (49.32%), 99 (45.21%), 87 (39.73%) and 60 (27.40%), respectively, for 400 ps, 600 ps, 800ps, 1 ns and 2 ns long transitions. The corresponding ranges of overlap coefficients are 0.00-0.05, 0.00-0.07, 0.00-0.08, 0.00-0.10 and 0.00-0.20. It is clear that an increase in transition length leads to better overlap which is expected due to smaller work dissipation, in turn leading to work values closer to each other in the opposite directions (also see Figure ). However, a significant fraction of complexes have zero overlap in all cases, going down to only about 27% even when using a 2 ns long transition, a value much higher than the transition length generally used in the literature. This doubtlessly contributes to larger uncertainties observed in general with the NEQ approach as compared to the EQ approach. Further, Figure displays the correlation between unsigned error (UE) and overlap coefficient for the entire dataset using the same transition lengths. We can see weak anti-correlation between these quantities in all cases which is expected given the necessity of non-zero overlap for unbiased estimates. More importantly, the majority of complexes with large UE are the ones that have zero or very small overlap coefficients. It should be noted that these values are obtained using an ensemble size of 10, replica length of 10 ns and 500 transitions at each end-point making our findings statistically robust.