Just in case anyone's curious, my new 27 arrived today. The 512 Blade is Samsung. I could never find any info on what the new 256 & 512 options were until I looked at mine. Same ol' but feels plenty fast here
Looks like Apple is still using the Samsung SSDs despite their rather shaky relationship. Can you run the Blackmagic disk test and see what numbers you get? My guess is it's still an 830-based part, but the numbers will tell us if that's true.