Sure, it takes more time than an attack or can. Some attack happen quickly. Not instantaneous quickly, but more quickly than you can draw two weapons. Other attacks are slower.
So we agree that a standard action which can also actually be something so quick that it can be done while moving or attacking is actually shorter than things can be done as reactions ?
Sorry, but once more, there are simple counterexamples to all your attempts at giving precise durations to any action or action type. None of your constraints are anywhere in the RAW.
What's not relevant is your argument about intervening space. The only requirement for an OA is "Left reach." Is someone teleporting away leaving reach? Yes.
Is someone disengaging leaving reach ? Is someone going invisible leaving reach ? Is someone using etherealness leaving reach ? All of these could be crawling away. Speed has nothing to do with it. Again, you would have to prove that it's the "speed" of teleportation (I'm using quotes) since you have been unable to prove that there is any definitive "speed" to teleportation, teleporting 5 feet in "an instant" with its casting time of one action is actually probably much slower than stepping 5 feet away) that prevents the OA.
Would that trigger the OA if an instantaneous effect could be interrupted? Also yes.
No, it would not, because it's the mode of travel that counts, not the alleged speed.
It's exempted from the OA because teleports happen too quickly to react to.
Again wrong, the PH says: "You also don't provoke an opportunity attack when you teleport or when someone or something moves you without using your movement, action, or reaction." Is someone pushing you causing you to move too fast too ?
sigh
Honestly, you are now fetching the silliest things just to be able to contradict the RAW...
We agree that the spell once cast is instantaneous. It has exactly two instantaneous phases
So it's indeed SPLIT into two (according to you, for me, there certainly can be three). Thank you for finally admitting this.
sigh
, the second of which starts a split second after the first one completes. Phase one is teleportation. Phase two is thunder once the teleportation occurs and the caster has disappeared.
So you have split an instantaneous effect into two instantaneous "phases", congratulations, you have contradicted yourself.