I agree it doesn't matter why it failed replacing it should fix it.
However it failed when just using my phone, not from flashing. Yes it can't communicate with baseband now. However I doubt the chip itself just "failed" I would put money on it being a cold solder, due to heat, flexing etc.
Hmm I didn't know you could "convince" apple to fix old iphones for $100 haha thats pretty good.
I am waiting for the beijing iphone repair place to see if they will reflow for me, or reball instea. When they replace the chips you get a Generic IMEI and serial which isn't ideal.