It’s because you fail to follow the trail of bread crumbs.
Iran’s military is not an open book like western militaries. Up until 2 weeks ago, no open source analyst knew that Iran had a flying wing design that could fly 1200 miles and drop weapons from an internal bay. It was suspected to be in development, but no credible evidence showing it was being made.
If you do some simple research you will see Iran trying to procure advanced fighter jet technology through espionage and procurement channels, including blueprints of F-35 engine.
Obviously Iran doesn’t need an F-35 engine to put into the Kowsar or any other 1970’s era fighter jet. Thus signs point to a covert aircraft development program that is seeking to develop an advanced fighter in the next two decades.
Now where F-313 fits in all this who really knows. It could be one of several prototypes under consideration. But I will be shocked if in 20 years Iran doesn’t roll out an advanced fighter jet. There are signs (ex IRGC involvement in Air Force = big money/brainpower) that Iran is taking a serious approach to the airforce, albeit a pragmatic and slow one.
Iran has learned long ago that if it is going to buy a fighter jet (Su-30, J-20, etc) it’s going to demand at the MINIMUM full production of all spare parts and engine maintenance and will likely ask for license production of the entire aircraft.
Iran buying a foreign fighter jet outside of these circumstances is unlikely (unless it’s a small token amount). Iran-Iraq war demonstrated if you can’t maintain your airforce fleet then you really don’t have an airforce.