That's why doing a bottoming is such a good idea. That way you don't have to make that judgement. The total destucturion is equal opportunity.
*****
To answer you question, I don't know if herbaceous plants work the same as trees, but I know with trees it's only the very outer edge that's live. Like when you clone and scrape down a level and then get to the white pith? In trees that white core is essentially dead heartwood and all of the nutrient channels are all towards the outer bark. There are layers like bark, then cambiem, xylem and phloem etc. layers.
I'd imagine canna plants are setup the same, but I'd have to do more research to know for sure.
But, assuming that's true, the location of your
massive stake screw probably doesn't matter all that much. It just matters if you do it (or don't do it)
(I still think you should wait out the results of this reckless behavior before committing to do the same to yours.)