To me it just looked like he split and just had all the same memories. That's literally what it looked like.The dialogue I quoted mainly ("I'm fine because you fixed yourself", which he has obviously not done yet), plus some things Russell said in behind the scenes material. It's clear to me that is the intention.
How else would you interpret it?
There was no other sign of 15 being from 14s future. That lone dialog sticks out like a sore thumb by itself. It might be RTD's intention but it didn't work onscreen.
I'm not really opposed to the idea though. Makes more sense about how 15 is recovered. Just not how it came across on screen though.