I wouldn't consider not remembering snippets of conversation a full-blown blackout. that could be a grey-out where it's a blur but you at least remember where you were and who you were with. Some people tune out what their spouses say in conversation even when sober, although I would never recommend that.
From my experience a true blackout is where you are missing hours of your life where you were apparently doing stuff out in public and you wake up someplace else with no idea of what you did or said. Frightening!