Jeez it was just a light-hearted comment. I think you can address your doubts about what I wrote with more kindness and less snark.
> None of them "churn".
By churn I mean "lose and hopefully be replaced". That definitely happens. Some brain cells die and are replaced, some live your whole life (or die first)[0].
The cabinet is just a simile for cued recall[1]. More recently learned/recalled items are remembered better (front of the cabinet)[2]. Recalling memories in a different context can change them[3], suggesting recall isn't a "read only" operation.