But, as we all know, it had been swept away by that time.
Claiming that we all "know" this may be a little strong.
This is true. And perhaps an expedient (if not precise) choice of words.
However, I should think that one must at some point decide which items they believe compleatly...and which they do not. For if you don't believe in anything, then you might as well stay home and look for the Electra at Disneyworld. The art is to not over-step in what you believe unquestionably.
As I have said elsewhere in the past, I have come late to this party. For a very long time I was a fence-sitter on the matter of the Niku theory....and for quite some time (x being equal to years) prior to that I even scoffed at the notion in total. I have never even been particularly enamoured with AE herself, what keeps me in the game is the mystery and the puzzle.
Although I admit to being quick to toss about possible scenarios (such as this last one), none are meant as 'this is definitely what happened.' (would hope I wouldn't be so silly as to say that, anyway) More the intent is to throw out ideas in hopes that others might add or subtract from them. In either event, I do so based on experience gathered from an entire career spent with the FAA and a number of years of professional flying prior (including a certain amount of formal training in celestial nav).
What is my personal baseline at present? After spending a great amount of time thinking it was all just fanciful at best, the more I examine the bits and pieces of other supporting evidence (period navigational charts, post-loss transmissions, island-found items, etc)....I have crossed the line, fell off the fence, however you wish to say it. I personally believe the Niku Theory in one form or other to be almost necessarily correct. And as you've said....in for a penny in for a pound. Once you subscribe to that general theory, there is no getting away from the swept away phase which would come at some later point.
Furthermore, based only upon available more recent photographs (which admittedly may therefore be misleading), unless there has been a radical change in the island shorelines I would be TERRIBLY surprised if they landed on any other location on the island. If I was over that island near low tide and looking for long, wide, smooth, and dry....that section of beach Norwich-to-Nessie (excepting the lagoon inlet) just screams at you. While other sections do not appear impossible, neither do they appear as good. And I certainly would not pick any other section just to lessen my walk to an observed pond of unknown drinkability. No...if I'm overhead looking to get down with the least amount of fuel spent and injury sustained, I would do exactly as I describe above for all the same reasons ...hopefully forgoing the ground loop of course.

....TB