I’ll make it simpler -
From a rivalry perspective - Pakistan is always looking to “see” what India does before it makes its move to get a capability a level above.
In this case - because the Indian fighter programs are being impacted by trade wars not just with USA/China but also Russia being completely out as a reliable supplier - combine this with supply/demand issues with Rafale - Pakistan planted the seed for panic with the J-35 announcement(whether it was intended with this purpose or for self promotion of the PAF chief is a debated topic) - now India was already in trouble and is now scrambling to find a solution for J-35 which is logically F-35 but it comes with many “hand cuffs” - the US wants it, there are those in IAF that are ok with it but with the F-35 India is permanently “beholden” to Lockheed Martin and the Pentagon regardless of assurances.
So, now that Pakistan has ordered the J-35(and it is expensive) - it is also trying to gauge India’s response -
1. Pakistan can get the WS-21 version - it has benefits in having common core with RD-93 full overhaul available. It will also give it an immediate edge but also gives India a target to best - after all aircraft are not like cellphones

that you can change every week.
2. Pakistan can delay induction a little and see if India responds by buying something under both actual military requirement pressure and political influence. Will it buy more Rafale? Will it buy the F-35? Will it buy a different fighter?
Once again, even with India’s deep pockets it cannot buy aircraft like chocolates and a purchase means a commitment for decades in terms of both funds and Human Resources. So once it pulls the trigger it has to stick to it.
The case here is - if Pakistan gets the J-35 it could likely have some land by late 2026 if it wishes with the WS-21. But the same money constraints India has Pakistanis have it even worse.
If they get a version now and commit to it - they will not have funds for a fairly long time to commit to another version of the J-35 leave alone another 5th generation project like the Kaan.