Yup, they can bow out. That is, you fundamentally changed it so why should they give you any support?
http://www.techradar.com/news/phone-and-communications/mobile-phones/here-s-why-sony-s-us-xperia-phones-don-t-have-fingerprint-sensors-1328799 and other reviews note the sensor isn't there so new firmware won't enable it since the parts are missing.
Hey guys! I've just purchased a sony xperia x (usa version). Because in the US, the fingerprint sensor is not working so I am thinking about flashing the phone to a uk firmware. I am just wondering if that is harmful to the phone? Also is it going to void the warranty? Thank you very much!