Most people have only vague memories before they're 5 or 6, so that's not so uncommon. I, an elder millennial, have lots of memories from before I was 6, but only because I have a big life event that happened when I was 6 that marked a "before time" and "after time" allowing me to easily place memories before or after the age of 6. All of my memories from the "before time" are vague and hard to place at specific ages except for a specific few that I can place due to houses I lived in at the time and what my parents told me.

I wouldn't say I wasn't self-aware in the "before time" but I definitely don't remember it as well as what came in the "after time". I'm sure that is what the above poster is referring to.