Have you ever woken up from a dream where you're sure you've forgotten 90% of it, but remember the portions most relevant to your reality?

No information has to be transfered in these cross-universe death/wake-ups. You can simply wake up with no recollection of the dream.

I'm not suggesting that branches containing separate information ever merge. I think my language was imprecise. I'm suggesting that one's perception of self-awareness and consciousness merges. The consciousness you have access to leaps to the next available branch.