This is bogus, and worse there is no way to turn it off. I work in Japan but many of my business contacts are in the US. No matter what I do there is no way to turn this "feature" off, and no way to stop gmail from adding a code to phone numbers.
Secret key downside may emerge for shifted reasons. It's wanting to be for Malware. Assume a system has been spot in from the transient net. http://robertbuckner.weebly.com/support-directory/gmail-care-helpline-call-1-866-688-6581-i-technial-and-non-technical-support