FrogReaver
The most respectful and polite poster ever
Per my post above, my interpretation says that actions don't have a duration.
No duration = instantaneous so we are in agreement there.
I think my building block analogy is the best way to describe the point I've been trying to make this whole time. If you assemble your turn as a sequence of basic building blocks, then there is never a question about "what's the duration of action X" -- a given action is just a discrete event in the sequence, and the sequence gets resolved in order from start to finish.
The issue is the attack action with extra attack. The attack action with extra attack is not a discrete event in the sequence you are referencing. It would be 2 discrete events, attack #1 and then attack #2. So then which of these discrete events do you assign the attack action to?
Edit: To be clear, I was trying to argue against the idea that actions last as long as their effects, because this doesn't make sense to me based on the Disengage and Dodge actions. There are more than two options though, and so I've given up advocating that since actions cannot last as long as their effects the only explanation must be that actions are instantaneous -- it makes more sense to me that actions simply have no duration at all, and your turn is built up of discrete strictly-ordered events.
#1 instantaneous = no duration.
#2 I agree that your turn can to some degree be described as being made up of a sequence of in gameworld events. Consider the following sequence: You move, you attack, you move again, you attack, you move again, you bonus action shove and then you move again. Each of those activities is a discrete event. If an action is a discrete event in the sequence then which discrete event described above coorelates to the attack action?
#3 the events on your turn can be strictly ordered and actions still being instantaneous. Consider the discrete event sequence: Move, attack action, shield master bonus action, attack #1, move, attack #2, move again.