In fairness then, yes, one has all of the legal rights of the an adult and the other doesn't. However, what dfference does this make, really. The age of consent is 16 so both are over it. I would be suprised if there is a big difference in matruity between the two, I know many 17 year olds who are more mature than 20 year olds.
In the end it's just one tiny year. That's nothing.
I certainly wouldn't say it's a "social taboo".