Looking at the Arduino UNO product page on this very site shows the SDA/SCL on the back like the original poster has. I doubt his was a counterfeit based off that information. Unless Arduino's own site is using pictures of counterfeit Arduino boards. I find this very odd considering their documentation clearly states A4/A5.
I am using I2C to communicate with a custom board and I can confirm those other pins actually do work as I2C. I was able to communicate with my custom board.