Extra rotor?

[BrianG]

Just got my T8 1700kv motor in the mail today (thanks Mike!) and was surprised to see an extra rotor in the box. I thought the padded package was some extra screws and stuff until my scissors slid from about 3" away into the package. Does this mean the existing rotor is the old style with potential issues and I should replace the rotor right away? Or is the included rotor a "just in case" replacement? A little confused here.