note that Iran is holding the other crew which means that the crew has information that Iran doesn't want to come to light. They may be able to buy their silence or get it with threats. Either way, a quicker release is better for the crew and worse for Iran.
I look for Iran to hold them as long as they can
The USN has released a timeline, which has some interesting information:
At 9:26 a.m. local time the Iranians requested that the motor vessel Hyundai Dubai, which had rescued the sailors from the M/T Altair, to turn the crew over to the Iranian FIACs. The motor vessel Hyundai Dubai complied with the request and transferred the crew of the M/T Altair to the Iranian FIACs.
At 11:05 a.m. local time USS Bainbridge approaches the Dutch tug Coastal Ace, which had rescued the crew of twenty-one sailors from the M/T Kokuka Courageous who had abandoned their ship after discovering a probable unexploded limpet mine on their hull following an initial explosion.
While the Hendijan patrol boat appeared to attempt to get to the tug Coastal Ace before USS Bainbridge, the mariners were rescued by USS Bainbridge at the request of the master of the M/T Kokuka Courageous.
So, Iran successfully 'requested' a hand over of the crew of the M/T Altair and seems to have intended to capture the crew of the M/T Kokuka Courageous, but failed.
Edited by Daan, 14 June 2019 - 1237 PM.