Apparently, SM does a revision of their contracts at the 5 year mark so the idols get more money for the last two years of their original contract maybe part of EXO's revision was an extension and they just didn't announce it... a 10 year contract is definitely illegal though the Korean government changed the law after the JYJ scandal.Yea some people said EXO's contract lasted 10 years, but apparently it's confirmed it's gonna be renewed this year so idk.
Maybe the 3 years are their trainee period gearing up for debut