I'm not 100% sure, but I wouldn't think that patterns count as CC in this case, even though they technically are.
The big fear, of course, is that CC will damage your game. And the fear is totally justified, because if the person making it isn't as skilled as they need to be, it can. But another major problem with CC items is that if you don't actually have it yourself and you download something that uses it (like a building), it will cause problems.
However, patterns are different. The easiest way to make them is to use the official Create-A-Pattern tool. And, if you download something that was redone with a custom pattern, it installs the pattern along with it. So (as it seems to me, at least), there isn't a whole lot that can go wrong in that case.
But it would still be best to wait on an official opinion.