I don't think the US sanctions are about denying Iran access to knowledge, but rather they are to deny procurement of technological assets. The Iranians already know how their current fleet works, they just can't get the parts for them. This aircraft is no use to them because it's broken, they can't get the parts to fix it and they can't use its parts to fix anything else. It's up to people on a much higher pay grade than us to decide what matters more - recovering a commercial aircraft that Iran could easily learn about by embedding technicians in the workforce of a sympathetic airline, or holding the line that sanctions will not be compromised, no matter what commercial interests (or common sense) may say.