That’s normal, it’s not a separation, but really just how the bed is manufactured; unless it’s made in 1 full piece it will have that gap. The lower cab side doesn’t help though. I resealed my whole camper. See my thread here. The bed seal I used came with putty and just shoved it all in there. Works great!
Edit: Realized it looks like you did the upgrade. Should’ve came with some putty. Easy to miss in the package, I didn’t find it 'til later and just shoved it in the cracks after it was assembled.