If I may opine on the Gs comparison between aircraft with my limited knowledge. Feel free to correct me if I am wrong but there are a couple of things that impact maximum Gs an aircraft can pull. For an apples to apples comparison, two exact same designs, say F-15A vs the latest F-15EX, the newer jet will be able to sustain more instantaneous Gs without damaging the airframe. Just like a human has to deal with the G forces, same applies to structures holding an aircraft together. Heavier metallic parts will experience more of a weight gain at higher Gs than lighter parts and thus composite airframe might do better due to their lighter yet stronger structure. JF-17 being a mostly all metal construction jet will have more parts prone to failure vs say a Rafale that has more composites and potentially lighter or better designed parts.
On the Gs themselves, any jet can be pushed beyond the max allowable Gs in an emergency situation, say when trying to avoid a missile or a collision. In those situations, it's worth the risk if damage to the jet and potential risk of injury to the pilot but to save his life. F-4s in Vietnam sometimes pulled in excess of 12Gs to avoid SAMs. The aircraft otherwise is rated as an 8.5G jet, and that too at in a clean jet with speeds below .8mach.
When you pull extremely high Gs, you could have the jet come apart in mid-air. And I bet you it has happened before. Rivets or glue holding parts will come apart, engine mounts could break, etc etc. If you do that in a jet that has fatigue built up already in airframe due to prior high Gs, you are at an even greater risk. This is the reason why air forces employ all types of methods and even built in sensors now to measure and record G forces and fatigue on parts. Fractured Mechanics is an applied science. Lots of info for novices like me out there.
https://flightsafety.org/asw-article/assessing-the-sensors/
The other thing to keep in mind in engineering itself. When designing extremely high performance things like fighter jets, every inch and ounce matters. If the idea is to stay within the confines of costs, capability and materials available, you design around those. Over engineering say beyond the parameters, say for 11G vs 9G means higher costs, more complicated design, all for a very marginal increase in performance. We already have a sphere where most aircraft operate most of the time and much smarter people then us have realized what is important in terms of parameters and current technology.
One last thing I'll mention here is an additional risk when pulling high Gs. It can often result in loss of situational awareness for the pilot and they can lose their life by plowing right into the ground as well. That's why the trend has been towards safety vs pure performance in the last three decades.