Since I didn't get a response to my question (either I didn't explain myself clearly, no one knows, and/or it probably won't make a difference) I went ahead and did the next best thing by doing an actual experiment to determine if there is actually a difference. I am still in the process of learning RF so take the following with grain of salt plus please point areas that need to be fixed. The driving force behind all of this is because I am having a hard time believing I am getting so bad of a return loss with such a simple setup.
I drew up a small PCB which is composed of two grounded CPWGs whose ends are interfaced to an SMA end-launch connector on either side. The actual footprint for each SMA connector is the same. The difference lies in the gap width between the connector's signal pin pad and the adjacent ground. The top two SMA connector's signal pin pad has a gap width that is the same as the gap width surrounding the grounded CPWG. The bottom two SMA connector's signal pin pad has a gap width that is larger than the gap width surrounding the grounded CPWG. The enlarged gap width for the bottom two connectors was determined by adding the diameter of the connector's signal pin to the copper thickness. Note that the ground plane on the inner copper layer closest to the top copper layer has been removed for both versions (top and bottom) and extends as far as the end of each respective signal pin pad's gap to account for increased in pad width compared to trace.
To solder the SMA end-launch connectors I used a clamp to ensure that each SMA connector was pressed tightly against the board so that the gap between board edge and connector was minimized. I tried my best to ensure that the signal pin sat flush against the signal pad but wasn't too successful as any downward pressure on the board would compromise the horizontal alignment.
After the application of solder-paste and hot air the board looks alright. Some free solder balls are present which will be cleaned off prior to actual testing.
A look at the solder running along the gap between the signal pin of the connector and its respective footprint pad.
S11 and S21 for the top trace with the unmodified gap width
S11 and S21 for the bottom trace with the modified gap width
Conclusion: Widening the gap between the signal pin pad and the surrounding ground plane results in actual appreciable improvement in S11 (about 5dB better) as well as S21 (less ripple). Since the signal pin pad's width is already taken care of by removing the ground plane directly below the pad itself in the adjacent inner copper layer, one can assume the presence of the SMA connector's signal pin contributes additional capacitance (lower characteristic impedance) to the transition point between the end-launch connector and the grounded CPWG. Suffice it to say, it likely won't be as forward as just adding the diameter of the connector's signal pin to the copper thickness for calculating characteristic impedance but for a pinch it may be sufficient. Next step would be to increase the gap further and observe its effects (transitioning from a grounded CPWG to a quasi microstrip configuration at the site of where the connector's signal pin interfaces to its respective pad).