I don't really follow your Cunning Action argument. The Bonus action granted from the Cunning Action class feature has no trigger, thus it can't be nested. The "on your turn" bit isn't a trigger, it's just a reminder of the scope.
I guess I don't find the contrast between "scope" and "trigger" very helpful for understanding or parsing these rules. I mean, I feel that I could deploy that distinction to say that the "scope" of the Shield Master bonus action is a turn in which the Attack action is taken - and that action is taken (although not necessarily
fully resolved, if I have an Extra attack) as soon as I attack on my turn.
And now there's no "nesting".
Conversely, I feel like I can insist that Cunning Action does have a trigger - to wit,
when you take a turn in combat. (Ie I can't take the bonus action, effectively doubling my speed, in ordinary movement situations.) And now there is nesting.
You can't simply assume people will reach a conclusion that fits your definition of reasonable or rational.
Of course not. But I can put forward what I think are good or bad reasons for various interpretations. Until [MENTION=205]TwoSix[/MENTION] provided me with the reasoning not far upthread, it seemed pretty clear to me that the attack action has to be taken to trigger the bonus action; but the inherent oddity of extra attack within the game together with the movement example makes it pretty clear to me that one takes the attack action by making an attack on one's turn, and then the
exra attacks play out in a rather flexible way, which if it can include 15' of movement can probably include a bonus action as well.
So if this gets characterised as "nesting" well I just don't see what the problem is.
Nesting doesn't seem to be a concept that occurs in the rules, or that one needs to explain or apply the rules. It seems to be an external concept introduced for the sake of tidiness.
Can a rogue who is Dashing as part of a cunning action drop something as s/he moves (but not at the beginning or end of the move)? I assume so - the rules don't contain a notion of "nesting" that makes me doubt it.
I should add - the oddness of Extra Attack is simply the latest example in a legacy of terminological and conceptual difficulties over what constitutes an "attack" that go back through 4e, and 3E's "full attack" that contains multiple attacks back to the rules in Gygax's AD&D which distinguish a monsters attack sequence of claw/claw/bite (ie three attacks) from a 12th level fighter's ability to take two attack sequences each of a single attack.
And these "nesting" worries seem very similar to debates back in 2008 about the proper interpretation of the OA-triggering rules for movement in 4e (where an example in the PHB of how taking the first square of movement triggers an OA even though the whole movement action hasn't yet been resolved). I'm not sure where exactly the concern comes from - for someone who's
not a programmer (ie me) it looks like maybe it's a worry about the clarity of the logic in an algorthithmic resolution process, and the possible risks of some sort of uncontrolled looping/recursion? - but I personally just don't find it a useful analytical tool in these contexts. Whereas
the text and
the gameplay context I find very helpful. (I'm not a programmer but I am an academic philosopher and lawyer, and when interpreting statutes text and context are the two most important things, whereas this "nesting" idea isn't part of the toolkit.)