Asgorath
Explorer
And the Attack action can equally be read as the DM giving you a token that says "you may execute all your allowed weapon attacks between now and the end of your turn"!
The fallacy you're making is Special Pleading. Actions either are ALL 'instantaneous, with ongoing effects', OR they ALL 'have a duration'. Saying that some work one way and some work another, without written rules, is Special Pleading!
NONE of them have language that tell you whether the Action itself lasts for its duration or is instantaneous with ongoing effects!
The rules are silent on this issue. This is indicative that 'when an Action ends', as opposed to 'when the effects of an Action ends', was not considered to matter as far as the rules are concerned. This leads to the conclusion that 'Actions are indivisible' was NEVER part of the design when written, and has only become a thing post hoc in order for JC to justify his change of heart.
Because, if it did matter, they would have made it an actual rule!
The Attack action says: "With this action, you make one melee or ranged attack."
The Dodge action says: "Until the start of your next turn, any attack roll made against you has disadvantage if you can see the attacker, and you make Dexterity saving throws with advantage."
One of these actions is an instantaneous event, the other action has a lasting effect. The Attack action is the act of making a weapon attack. The Dodge action provides a temporary effect that lasts until the start of your next turn. The building blocks you assemble your turn out of have the action as a discrete event in both cases, but one explicitly grants a lasting effect and one does not.
I'll just stop at this point, as there doesn't seem to be much point in continuing to try and explain how the combat system works in a way that is consistent with official rulings on the matter.