DJI is obviously aware that there are bugs in their code that can result in a crash and destruction of the drone. It is why they have the 12-month replacement program in place. If their aircraft were reliable and had failure recovery code then they would not need the program, nor would their customers.
Reminds me of when in the 1980's Chrysler started offering warranties that were twice as long as their competitors. It was the only way they could get people to buy the very unreliable cars that the company was making. The top management decided it was more profitable to provide the longer warranty coverage than to improve the quality and reliability of the vehicles.
A 12 month warranty is normal industry practice. And DJI reliability is really quite good - certainly the number of losses that get posted about on this forum that turn out to be aircraft failures is very small.