But that is the only leverage Iran has, and the article 5 of MOU clearly states:
"5 — Upon the signing of this MOU, the Islamic Republic of Iran will make arrangements using its best efforts for the safe passage of commercial vessels with no charge, for 60 days only, from the Persian Gulf to the Sea of Oman and vice versa. The traffic of commercial vessels will immediately start, and considering the need for removing the technical and military obstacles, and demining by the Islamic Republic of Iran will be instated within 30 days. The Islamic Republic of Iran will conduct dialog with the Sultanate of Oman to define the future administration and maritime services in the Strait of Hormuz in discussion with other Persian Gulf littoral states in line with the applicable international law and the sovereign rights of coastal states of the Strait of Hormuz."
By directing shipping traffic to the Omani side of the Strait of Hormuz under US protection and without consulting with Iran is a clear violation of article 5 in that agreement.
And with such background, not sure how you can make the case that "There is no justification for Iran to target commercial ships passing near Oman".
Remember, the dispute is not between Oman and Iran; it is between Iran and the US, where on the US side a guy named Bitchjamin Satanyahu is calling the shots.