That is entirely not true - no one remembers every detail of their life. As for the ones who do, you can do a fairly good impression thereof by simulating reliable synesthetic associations.

I don't remember every single detail, but I have clear memories from before I could walk, like watching Wizard of Oz on VHS and not being able to walk away even though I was tired of watching it. My wife says she doesn't remember anything before about age 5.

I think that for the case of the Turtle - early childhood memories would actually have a larger impression as everything about them is new making them have a bigger imprint where as there mid 80s - 150s range is probably one giant blur of repetition.

Imagine being a software developer for 200 years? Oof you would be such a crank/skeptic having to deal with all the tech changeover