Optional properties get unwanted default values in memberwise initializers

I had this same opinion a year back. Ever since, I've come to understand the issue as @xwu poses it, and arrived to the conclusion that it's better to remove implicit behavior altogether, in order to comply with Swift's core ideal of clarity over brevity. Introducing more rules to the exception is not the way to tackle this issue. We ought to get rid of the exception in the first place.