Yes, I am a native speaker. We use inversion for questions, but not all the time- you can make pretty much anything a question by a rising intonation- if you say 'really?' with the correct intonation it is a question, and it's unnnecessary to make a complete sentence out of it.
Are you sure about that?
You're sure about that?
You sure about that?
You wil here all three being used. The last two are far more likely to be used when the speaker is surprised by what the person has just said.
