Yeah, this was the long taken approach in which each agency/user would do trials individually themselves that too in a linear fashion with no concurrent testing for different taking place simultaneously
That is not true. For a big project like Jet development, each supplier has its own contact within the project development team, for example, the vendor of radar will deal with the chief engineer of electronic system, the material suppliers will report to the head of body structure sector. Whoever is ready, the leader of the corresponding area will host the trial and conclude the result. So there is no way that the test of different subsystems can be done linearly.
The internal trials of agencies is their own problem, running with their own schedule.
indigenous products are also taken up to meet very strict requirements with little to no room for concession. There's a reason testing in India takes so goddamn too much and the reason why I fume when foreign maal passes trials with so much ease.
There is no evidence suggesting that India is requiring more tests on similar products than foreign countries do.
The only reason is that Indian scientists have less experience than their foreign counterpart after all a lot of weapon projects are first time for India. Less experience means more mistakes, certainly you have to repeat some tests to prove that mistakes are fixed.
So, previously drdo would do internal trials, then IA would do trials of the prototype and if it passes the parameters than IA would do trials again of the production stage product made by some psu or cos to see if that stands up to same parameters. Would like to be corrected but that is more or less how it goes.
It is a standard procedure of new product development in EVERY country.