I kind of doubt it: those sanctions were lifted via "temporary" reprieve almost as soon as they were imposed, and the thrust of those sanctions did more to block US suppliers from exporting to ZTE than vice versa. It's equally likely that ZTE is just staggering the global rollout to keep supply and demand under control, and starting with Europe because who wants to deal with US carriers if they can help it?
Because, say what you want about them, Samsung just knows a lot more than most OEMs about how to tweak smartphone camera mojo. And ZTE has much, much less experience with flagship-level devices than Samsung.