Hriston
Dungeon Master of Middle-earth (He/him)
When reading the PHB without the 'benefit' of the tweets/Sage Advice, it is just as reasonable to interpret 'when/if' to mean 'when/if you take this action this round', so both Action and bonus action must be chosen together but the timing withing the round of the execution of each element of those actions is up to the player.
How do I know that this interpretation is 'reasonable'?
Because that is the interpretation and the intention that JC himself had from the time he wrote the PHB until the 2017 errata.
I agree! Jeremy Crawford told us what the RAI is on this at least as far back as 2016. His more recent clarifications of his interpretation of the RAW doesn't change that intent. It just means that, unlike in certain other instances where the RAW was judged to have failed to convey the intent and was acknowledged as errata to be corrected, in this instance even though he admits that according to his interpretation the RAW has failed to convey intent, the corrections required would be too sweeping to undertake.
As for me, I'd much rather go with what some consider to be a strained reading of the rules and play the game as it was intended to be played than be bound to an unintended consequence of how the rules happen to be written. Fortunately, we are all free to make this judgment for ourselves!