Honestly, i disagree. The J-10 would have been an entirely new aircraft for them to learn with a weapons ecosystem they arent familiar with or have an ounce of in their stockpile and would have taken a tremendous amount of time to acquire in numbers,especially as they would be behind China and Pakistan in getting their jets. Then when they have them, would needa huge length of time to integrate them into their fighting force (as you yourself always point out, integrating a new fighter type takes up to 3-5 years). By the time they negotiate a deal for J-10,acquiring it and integrate it into their forces in an effective manner, the KAAN will be almost ready for production. And these fighters are meant to be a stopgap between the fleets current conditions and the arrival of a FGFA to hold the line against Greek F-35.
With block 70,they not only integrate near instantaneously, but they get to upgrade their own existing fleet with Ozgur radar, dramatically increasing their fighter capabilities in a much shorter period. Additionally they would face increasing isolation, especially in NATO for operating non-NATO equipment. Currently they still have a great deal of cooperation in NATO despite the S400 issue.