normally this is true. I replaced the faceplate on my z520a and the earpiece stopped working. $50 insurance claim... ouch. I think it's to avoid someone trying to hack the phone or, like Tim Allen, give it more power and then screwing up their phone and trying to blame it on some faceplate sweat shop mess-up. or if got dropped and the screen cracked, nope it happened while getting the faceplate removed.