Let's put it this way on my theory on defol. I defol for light and air flow. I'm always, unless I experiment, gonna LST. Using those parameters, it maximizes the amount of leaves dedicated to photosynthesis which in turn goes into growing bud.How about this. In my never to be humble opinion and my limited six years experience with growing autoflowers, it's a myth.
Sorry I don't know how to add the funny figures or abbreviations. I'm an old.
The true question is this: Does the energy gathered for bud production by limited defol, exceed the energy expended in new foliage is offset by the possible hormone production for bud expansion in response to the "Fight or Flight" induced by heavy defol.
This is assuming canna has a sorta similar response to such stressors as other garden vegetables, such as beating your indeterminant tomatoes to induce blooming.