Plausiblity is only good if you can deny them. Again, do you think they went through all these attacks and then just leave it at the "possibility" that the facilities were destroyed?
The core issue is, if they think the Fordo complex was not destroy, if there is a possibility in this realm, they will go at it again, they don't do all that to just let Iran get back to enriching Uranium on the download. Those day were gone, there weren't direct attack on site like this before, sure, they hit Iranian power plant and kill Iranian scientist, but never going all these extreme just to hit the 3 site they did. And that's not Israel doing it too. I
So the answer to you question is, do you think they will take Iranian word for it and stop attacking you? Or do you think Iran can somehow keep enriching uranium on the download from now on with Israel and US at their back? That is the actual question you need answer to.