Hi Deciacco
Firstly, considering that you're getting better mileage and the bike is smooth, I believe your TBS was on point, and that should not be a consideration of what's happening.
With your findings, we went out to our in house 1200GSA as well, and noticed firstly, that we will need to do a TBS on ours to get low idle RPM (ours is constantly at around 1350RPM with or without clutch/neutral).
What we suspect is happening, is that the RPM default value for neutral and clutch in is set to 1100-1200, which is normal after the TBS, and once clutch is detected as released and neutral is no longer present, it comes under load, so works a little harder (i.e. giving a bit more fuel/air to sustain RPM). An example of this would be standing still and starting to walk, or walking and then walking against a slight incline.
Nevertheless, I don't think this is something to be concerned about, given that with the clutch switch removed, the bike thinks 1500 is the target RPM even with the clutch pulled in, this supports the opinion that the bike's target RPM should be reached at all times with the exception of clutch in (not detected with the switch removed) and neutral.
Hope this helps!
Kind regards and safe travels
Ruan