Well if Turkey had brought the jets back home, the biggest benefit they'd bring is;
1_) For TAI to be able to inspect the whole aircraft they've built important components for, so that they can get a better understanding of "what makes a 5th gen, a 5th gen?"
Meaning: Being able to throughly inspect the whole aircraft and being an important industrial partner of the program are not the same thing.
2_) what tactics to employ against enemy low observable aircraft (F-35 in particular, some of its users are quite antagonistic towards Turkey).
At the end of the day,, Turkish institutes still managed to learn how to design and build a fifth gen thanks to their contributions to the JSF program, but they'd have gotten a better understanding of their capabilities and doctrinal usage if both TAI and TurAF had been able to use and inspect it.
3_) Kaan wouldn't have become a heavy strike aircraft at the last moment to cover both it's original intended role and F-35's role; instead it'd have stayed as a nimble, J-35A- and KF-21B3-class air supremacy fighter.
@TomcatViP Mind you, TurAF chose to be a part of the JSF program, those 6 built-and-delivered F-35s had already been inducted by the time Turkey got kicked out and
technically, they still belong to the TurAF; US is just not letting them fly to Turkey.
4_) Turkish Navy wouldn't have to take risks and relentlessly pursue MUM-T and unmanned naval aircraft this early and build a dedicated 60.000 ton aircraft carrier for them.
I've already written a lot about this topic but Turkey getting kicked out is not entirely Erdogan and his government's fault either:
https://www.secretprojects.co.uk/search/1227685/?t=post&c[thread]=17732&c[users]=snne&o=relevance