I got a greatest hits req pack?

Ok so yesterday I went onto my reqs (on Halo Waypoint) to open my daily pack. When I got there I was surprised to see that I had a Greatest Hits Customisation Pack for free. Anyone have any idea why? I though this was an exclusive pack from like a year ago. https://cdn.discordapp.com/attachments/359348449637957636/373588106625941506/image.png https://cdn.discordapp.com/attachments/359348449637957636/373588124376498178/image.png