It's not about Blindly Believing what the Other Side thinks. It's about Knowing what your enemy is thinking and never underestimate him. I accept that JF 17 block 3 is inferior to SU-30 MKI. But JF 17 block 3 has PL-15E which is having range of 145 kms(Let's take it for the sake of Argument). So I guess in terms of overall BVR range ,JF 17 block 3 has a Slight edge(If we take this claim of Pakistan Seriously atleast for once)
Other than that SU-30 MKI is superior in every aspect. I want to see Super Sukhoi happen, I want SU-30 MKI to have MAWS and get new BVRs(Astra MK-2)in it and finally we can close the Gap between JF 17 block 3 and SU-30 MKI.
Oh, we overestimate them, believe me. They underestimate us, and their ego has been inflated just because they scored a kill on a Mig-21.
JF-17 Block III has PL-15, correct, but it is not in active service yet. Astra Mk-2 is 150+ km range with a minimum NEZ of 80+ km and is scheduled to be inducted within 2-3 years when JF-17 Block III will be in PAF.
The second part, Chinese BVR (PL-12/SD-10) is reportedly underperforming and nowhere near its original mark. There is no reason to believe PL-15 is going to be effective either.
JF-17 is a cheap, 4th gen light fighter. In an overall fight, it might be able to score a few kills, but it will be the slaughter of PAF in aerial battle if they keep on relying on it.