@sevem47 ,
Sorry, as you can see, I figured that out after I asked you the question.
If I set <Standard hideAll="no">, but then manually set <Button hide="yes" for all the standard buttons, and then set hide=yes for particular buttons, I can get it to hide all of the standard buttons and select of the plugin buttons. You can use that to implement what you want.
62484fd6-39b8-4ac2-ac5f-7c4bd93f4430-image.png
So @donho, the <Plugin ...> section bug only shows up if <Standard hideAll="yes"> ; if you manually hide each individual Standard button, the <Plugin ...> section settings work correctly. Hopefully, that will help find the logic bug.