I've been reading most of the posts on here about having to export NEF/RAW files from Photos to a separate folder then import from that folder into LR CC. That does work, but is a tedious step, IMO. It seems like the problem is that Lightroom CC just imports the thumbnail (jpg) from Photos. When you try to add an image directly from an album in Photos into LR CC, it will pull the image file from the "derivatives" folder (all jpg) within Photos Library, and not from "originals" folder (where the NEF files live). Hence it comes in as a much smaller jpeg than the NEF file you want. I'm hoping that someone else can confirm this and that Adobe can diagnose that problem and correct it.
Feature request, Import and share, Problem or error