Another way to look at this is Apple isn't putting in the right sized batteries in their phones because they believe thinner phone is a better phone. If all it takes is one year for the phone battery to stop providing enough juice to the CPU/GPU then either the battery is not of adequately designed capacity or the CPU/GPU has too much peak power draw for the battery.
Either way looks like a design issue that's just too convenient for Apple to keep selling new phones each year. If they put slightly thicker battery with adequate spare capacity or reduced peak power draw for their SoC people can get 2+ years of consistent performance out of their device. Instead Apple is designing to provide one year of peak performance followed by slow downs so you can go out and get the new phone next year - sounds not very user friendly to me no matter if it looks intentional or not.
Either way looks like a design issue that's just too convenient for Apple to keep selling new phones each year. If they put slightly thicker battery with adequate spare capacity or reduced peak power draw for their SoC people can get 2+ years of consistent performance out of their device. Instead Apple is designing to provide one year of peak performance followed by slow downs so you can go out and get the new phone next year - sounds not very user friendly to me no matter if it looks intentional or not.