For those who don't know, the original Relapse 2 was ready to go when the first was. In terms of, the material was all there, it was all recorded in the same sessions.
But 50 even said, at that time, that the first one was a "treat" but the second one was "exciting". So even if it wasn't totally polished, it was pretty much ready to go right away. He must of had it mostly compiled.
Now obviously, he would of put the best of the material on the second one. Or at least... The most compelling. So 50's comment isn't all that surprising, you should / would expect it to be that way. Save the best to last. Em also said that putting out the second one would allow everyone to get "all of the best stuff". Obviously meaning that with both albums but...
Aside from the Refill tracks, that means the best was yet to come from the Relapse sessions and we'll never hear those tracks now. As Recovery is totally new material, he just made a new album after he started going in a new direction.
So think of that. As good as some of the Relapse tracks are, those were the LESSER of the two batches. We heard the weaker of the two albums and won't ever get to hear the strongest. I find that really annoying lmao. He could of just put out Relapse 2 as it was and done Recovery as he has now anyway.