An other compatible explanation is that they wanted ambiguity about their weapon production.
Besides, wasn't this whole thing triggered by a UN report showing they had made a lot more 50% enriched stuff than expected? I.e. the monitoring "worked"
But ambiguity with respect to weapons production has to be taken as a confirmation of an intent to develop weapons of the opposite side. Which makes this equivalent to just having a nuke program. It doesn't even give you a bargaining chip because there is nothing you can do as a step back (since you didn't do anything in the first place)
Besides, wasn't this whole thing triggered by a UN report showing they had made a lot more 50% enriched stuff than expected? I.e. the monitoring "worked"