In part designed to keep Israel at bay. Israel knows the condemnation they’d receive if they were to begin a campaign of deconstructing Iran’s facilities while negotiations are in progress.
Delay, stall, capitulate and delay again.
The Persians are playing our negotiators like a cheap fiddle.
I don’t doubt your stated motive for the delay tactic (stalling Israel), but the tragedy is that US is still determined to sign whatever pathetic agreement oozes out at the end of the process. I suppose that’s what they want.
I think our "negotiators" are really working with the Iranians to assure that Iran has the time and resources to attack Israel and then the rest of the West. There was even a report posted some time ago on FR that the French said the US representatives were acting more like Iranian representatives trying to convince the rest of the Western negotiators of the Irnian position.