Actually, I listened to an interview with Marandi in which he actually said that Iran's negotiators came up with a very clever way to make sure US doesn't leave the deal this time.
In short he said Iranian negotiators fully expect the next President to try to pull out of the Iran deal again, so instead of relying on the Americans, Iran itself inserted a clause into the agreement which basically will allow Iran to rapidly enrich uranium to weapons grade as a consequence if US were to leave the deal this time and this is written into the agreement explicitly. This way, Iran does not need Congress to pass it as Iran itself will impose a cost on the US if they try to do it. If any Republican President tries to leave it, they will be forced to allow Iran to rapidly enrich uranium to weapons grade, even Republicans don't want that so they will be forced to accept it.
The potential trick with the US not leaving the JCPOA is that it may then act like the Obama regime: impose new sanctions under pretexts other than nuclear and thus discourage companies from trading with Iran, while at the same time pretending they are still participating in the deal...
If as a consequence Iran decides to walk back on some of its own commitments - something the JCPOA does allow explicitly in fact (by stating that if one side fails to fulfill its duties, the other can do so as well), the US could invoke the Dispute Resolution Mechanism (DRM) enshrined in the document, by complaining that Iran is violating the terms of the deal. The DRM specifies that several rounds of talks must be held to try and solve the issue, but that if no solution is found, the plaintiff can refer Iran to the UNSC, where UN sanctions are then automatically snapped back without even a vote - meaning Russia and China would not be able to veto it.
Whereas if Washington outright leaves the JCPOA like Trump did, it will no longer have the possibility to initiate the DRM, and therefore to have UN sanctions reinstated as a result.
Now of course, even if they leave the deal, which will allow Iran to scale back its commitments as per actual JCPOA provisions, the Americans will still lie and claim Iran is "violating" the agreement. Which is what Trump also did, however he had no way to achieve UN sanctions snap back.
So, while what you describe is indeed an important bonus for Iran, guarantees that the US will not go the Obama route are just as important - i.e. that the US will not officially stay in the deal but effectively violate it to prevent Iran from reaping the promised economic benefits, while maintaining the option to provoke UN sanctions snap back in case Iran reacted accordingly. However from what I heard Dr. Marandi say, it would seem that Iranian negotiators have submitted firm conditions in this regard as well.
