I do not agree, plugins do not work that way (and you know G’MIC like no one else, so for you it’s natural ).
For example, take any GIMP’s plugins:
You input your setting first, then when you have finished, you click OK, you will never click OK before applying your settings
Most of the filters in G’MIC (~90% ? ) are applied when we click OK (I don’t speak about the Apply button), also when we click OK, that OK button closes the G’MIC’s window (in 90% of the time) which is expected by the end user as a standard behavior and even encouraged by G’MIC 90% of the time.
So even G’MIC in ~90% of the cases, tells you “click OK when it’s done”.
Then we have ~10% filters filters which need to be called with the OK button…
Behavior expected by the end user (at least me for many years or first comers to G’MIC)
“this filter does not work, I click Cancel or the close button on the top bar to not affect my picture in GIMP”.
Yeah… A note telling us to click first on the OK button first would be more than useful in these specific filters
Note: I have no idea about the percentage of filters which start with OK, numbers are just for example purpose only