There's no sense in getting too mad/offended at what people say just because they're ignorant. My older brother and I have a different biological father than my two younger brothers. We've never considered ourselves "step" brothers, but once somebody said "oh, you're their step brother?" It was really weird for me to hear this, but that's how people think. And indignant correction would've just made me come across as a hothead. A gentle correction just seems much better to me.
On that note, congrats on the new daughter Sobo! My coworker and his wife are at the end of the process and are looking to travel to China this summer sometime to pick up their daughter.
And, my mom was in Vietnam and ran into a French lady who had been in the country for 4 months getting the runaround trying to adopt a child