Hmmmmmmm....
The more I think about this relaxed/natural topic, the more I'm starting to believe that the whole "natural is unchanged" theory is quite flawed.
Anything that is natural can change over time. For example, the skin ages and wrinkles, but does that mean that the skin itself isn't natural because it isn't as youthful as it once was? The terms "Natural" and "Original" are not the same thing. Natural relates to nature, the physical world and life--the absence of artificiality. To say that someone's hair is not natural, is implying that their hair is synthetic, man-made or being grown through and with artificial means.
When a person relaxes their hair, yes the curl pattern is destroyed, but the scalp in which the hair grows from is still natural because it continues to grow and produce hair in its original form. Also, we often forget that once the hair leaves our scalp, it's dead. And anything that alters something that is already dead, doesn't really count as anything, because it's dead.
So, just because something changes, doesn't make it any less natural. As a matter of fact, change in itself is a natural process.