Very straightforward auto action to get an exact selection. This has been useful for me, and maybe it will be useful for you as well.

Sometimes [ctrl + click] on a layer doesn't actually select all of the pixels because of the transparancy threshold.
In those instances you can use this auto action to create a selection layer with all of the pixels selected.

Sometimes [ctrl + click] on a layer doesn't actually select all of the pixels because of the transparancy threshold.
In those instances you can use this auto action to create a selection layer with all of the pixels selected.
then you can ctrl click that layer to get the true selection.

compare that with the original [ctrl + click]

It has worked for me whenever I needed it, but results may very.
Run the auto action on the active layer.
This will create a temporary layer called "layercopy" which it will delete afterwards.
Ensure no existing layers have that name or it may bug out.