That's right. The matches from Gmail are collapsed unless you specifically indicate intent with search keywords like "gmail" or "email."
Non-tech users (probably 95% of Googles customers) have no idea how this happens. It's not immediately obvious to a non-tech person how your personal e-mails suddenly get blended into search results on another page. This will both freak people out and it will invade their privacy.
I really hope this will be opt-in.