When an interpretation requires Schrodinger's actions and/or time travel in order to work correctly, it's the wrong interpretation.
		
		
	 
Really? On page 98 of this thread you gave a rules example that works this way:-
	
		
			
				Maxperson said:
			
		
	
	
		
		
			This is essentially the same as when I look at the rule in the PHB that says that after you reduce a creature to 0, you can retroactively decide that you were knocking it out. I think it's wrong and a bunch of malarky, so I created a house rule and changed it.
		
		
	 
Whether you (or I) 
like it or not doesn't alter the fact that many D&D rules 
do work that way!
Other examples include:-
* various abilities (orcs, barbarians, zombies, etc.) where if you get reduced to 0 hp, you have 1 hp instead
* druids being 
disintegrated, then 
reintegrated
* the 
shield spell triggering on 
actually being hit, and then 
changing that to 
not being hit
All these things 
seem like 'Schrodinger's Actions' or like time travel. But, crucially, only at the table, 
not in the game world!
Sure, at the 
table it seems like:-
* you attack a creature with deadly force, killing it, then decide you want to keep it alive, then go back in time to deliver a knockout blow instead
* an orc/barbarian/zombie gets killed, then 
heals(!)
* a wildshaped druid gets turned to dust and then the dust turns into a druid
* a javelin goes through a wizards head with enough force to kill him. He 
then casts a spell and time rewinds, and 
this time the javelin misses
But there is no time travel ret-con 
in the game world at all:-
* you knock out a foe, just like you meant to all along
* a blow that 
should kill an orc/barbarian/zombie fails to, because it is so darn tough!
* a wildshaped druids animal form takes enough damage to that form that he is forced back into human form, as is normal, but he was never actually 
disintegrated 
* a wizard gets a javelin thrown at his head, but casts 
shield just in time!
So, with Shield Master and the "If you take the Attack action on your turn" condition, and take the bonus action shield shove first, at the 
table it might seem that you 'take the Action' and then go back in time to take the bonus action (although that is a flawed interpretation of that condition, which I'll analyse in my next post), but 
in the game world you do as you have been trained, which is to deliver a combination of weapon attacks and a shield shove, by using the shield to knock a foe off balance (depending on the result of an opposed roll) to give you advantage on the follow up attacks.
Nothing has gone wrong. There is no time travel malarky 
in the game world, only the game mechanics at the 
table which work this way, a way that is common in the 5e rules.