Since my other reply was flagged, and I'm past the edit window, and I learnt a little more about the nuance:

- Technically Iran was considered to be meeting the requirements of the JCPOA during the 2016-2018 period in reports issued at the time.

- Iran failed to declare all its sites and programs before entering the JCPOA. This is known now, after the fact.

- Technically some argue that because Iran participated in meetings and filed papers they met the PMD requirements which were the preliminary requirement for the JCPOA to take effect. The nuance here is whether they technically fulfilled the requirements despite lying and hiding and then "only" violated the NPT or whether they violated the PMD.

- That Iran hid sites, material and equipment came into light after the Mossad stole Iran's nuclear archive. This is fact and was confirmed by IAEA inspections despite Iran's attempts to prevent that.

- When the IAEA asked to inspect those sites Iran engaged in a cover up operation and delayed access. After the sites were inspected there was evidence of nuclear material made by human activities.

- That material discovered by IAEA was not farther enriched which the supporters of the agreement claim is evidence that Iran didn't enrich more material. In reality Iran lied and hid facilities and so despite the samples taken by the IAEA not finding evidence of more enrichment the basic fact is that Iran acted in bad faith and so we just don't know. Maybe they only hid sites, equipment, and nuclear material but did not pursue further enrichment during this period. Maybe they did in other sites.

- Officially Iran was never found to be in violation of the JCPOA.

- The JCPOA was set to expire in October 18, 2025 after which there would have been no restriction on Iran anyways. That's another part of the argument that this was a bad agreement.