From a practical standpoint, I suspect the writers are trying to kill about ten birds with one stone.

By implementing the bit about the warriors of light being unrecallable in memories, it means that NPCs can treat surviving characters exactly the same as new characters when speaking to them in dialogue. It even further removes the need to worry about flags that differentiate mere meteor survivors with those that progressed to Killing a Raven.

This reduces the amount of text you have to write (and localise) to a small fraction of what it would otherwise be.

From a loremongering perspective, I imagine there being some interesting moments where I scream out "BUT DOOD, THAT WAS MEEEE!!!" and I'll be intrigued to see how they handle those moments.

The beta also makes a point about no one having a consistent story about what happened in those final moments. Unpicking this is clearly part of the main story, so I'm going to withold speculation until I've experienced it. Then we'll see what gaps remain.