I don't think you and many others in this thread understand what illegitimate software can be. You don't literally own the code on the disc you have. You own a license. When the store did not ring up your purchase until launch day you were not authorized to play yet as you did not own your license yet. This was a known agreement between you and the store.
This means that you were in fact playing an illegitimate copy of the game pre launch and now you have a legitimate copy post launch. It would be like me preloading a PC game, cracking it and then getting banned. I didn't own the license until launch but I still had access to the code. The main thing you keep missing is your paid license didn't start until launch day.
Look, NO.
It would be nothing alike.
Changing your internet connection proxy to be forward in time to unlock it would be comparable. And even then, it's still not alike.
Let's make this pretty clear: Microsoft is banning because they want.
Because they want and no other reason at all. They can have ways of preventing this from happening yet what they want is to ban pirates, even with collateral damage.
Let me tell you two solutions at the top of my head.
1. Game can't be played online (as in, online status) as it has the launch day coded into a small file and will contrast it with the LIVE servers (can be played offline).
2. Only people in the whitelist are allowed online pre-launch.
Do you think MS can't do this? As I stated previously, they use this to get pirates, because they have no actual proper tools of detecting some of the mods unless they do something stupid like modding lobbies or alter avatar colors.
PS: Sticker says DO NOT SELL. I don't see DO NOT BUY anywhere.