I think the claim as written is dubious, but the point is that our capacity to store information far exceeds our ability to recall information, and we can effectively recall things only because we forget so much.

There are a few people with a condition called hyperthymesia, like Jill Price, and the condition generally has a profound negative impact on their lives.

..and I wonder for people affected by hyperthymesia if they have memories of remembering a memory

I've remembered remembering things before. It's often been useful, especially when I forget the thing I remembered.

I don't find it entirely implausible. Think of it like bloom filters or floating point numbers; the more you need to store and recall, the less accurate it will be.

Its not like there's an "erase" routine in our brains, it's just that the neural pathways start getting used more and more for other more important things. But there's still a readable trace of the old pathway there.

Sort of like the shortcut over the corner of the lawn where the grass can't grow because everyone goes there, but then when the new overpass is built people stop going there and new grass sort of grows over it but not completely because other people see the desire path and use it for other purposes every now and then so it never really disappears.