As posted here on BF over the last several years, Fallkniven has had some very variable finish/quality issues with the ceramic side of their DC3/DC4 stones. Many had complained about the 'wavy' or swirly character on some of them, and I'm sure at least some of those were returned to Fallkniven for refund or warranty replacement. I'm not really surprised if they're trying something new; they need to find something consistent in their manufacturing process that works.
I've had a DC4 for a few years, and just recently lapped mine to a more uniform and somewhat less aggressive finish than when it was new. It's a better finisher now, than it used to be. When new, mine appeared to look like the one shown in your 2nd photo. It didn't have the 'wavy' appearance as in your 1st photo, but it was pretty coarse and irregular as felt under the blade's edge, and I never quite got comfortable with that. After lapping it, it's more similar in feel & edge finish to Spyderco's medium (brown/grey) ceramic, and I have more confidence in it now.
David
