The Indian designers are trying to mirror the USAF programs:
the FGFA will be the F 22
the AMCA will be the F35 for the IAF.
That's possibly what DRDO and ADA had in mind and what the common mistake is, because that is based just by the fact that we would have 2 x stealth fighters in different weight classes, but it completely ignors the different requirements of IAF and USAF or that F35 and AMCA will be completely different fighters too!
1. F35 will replace nearly all older types of aircrafts in all US forces, that's by far not the case for AMCA because it will be just a minor and operationally not needed addition to the fleet, since IAF will have FGFA, Super 30 MKI, Rafale and LCA at the same time!
2. F35 is meant to be a cost-effective low end alternative, to the more capable F22. That's why it won't have all the latest features a 5th gen fighter actually should have (SC, supermaneuverability...). That again is not the case for AMCA, because apart from the weight class, it is planned to get any feature FGFA actually offers too, which doesn't make it really cost-effective.
3. Operationally, F35 is highly aimed on strike capability contrary to F22 that has Air superiority as the main goal. FGFA and AMCA on the other side will be developed to have a more balanced multi role capability. Both will have good flight performance, carry many A2A but also A2G weapons, which again makes them completely different from the F22/F35 idea.
The only need for AMCA will be in IN, since it has no 5th gen fighter selected or under development yet, while IAF with already 4 x different types of fighters selected for the next at least 30 years don't need it. It would be easier and more useful to add more numbers of MMRCA, LCA and FGFA + developing armed drones and UCAVs, instead of inducting another fighter, but it's doubtful that IAF will just look and see IN getting an indigenous fighter that they don't have, even if they don't need it.
Wrt the topic, it's actually not surprising since Russia and India are known for delayed programms and if the US have so much trouble with their stealth fighters, it should be clear that we will face even more problems in the coming years too. Around 2020 was always the more realistic timeframe and it still needs to be seen what kind of changes India requires compared to Russia.