[mothered]

Well, I guess that's just having good luck. Although I think the risk is lower when ordering from Amazon instead of ordering from Apple directly.

Yes, It's less likely to happen with Amazon as opposed to the manufacturer of the device.

Let's just hope it doesn't happen. Yet, if it does, can I still unblock it somehow?

It can be changed, however the TAC (Type Allocation Code) which Is the first 8 digits of the IMEI number, Identifies the model & manufacturer of the device.

This means, If you spoof/change the IMEI number It will not be dedicated to the device and upon activation with a given carrier, It may well be rejected. That said, It will work with carriers who neglect to check the device It belongs to. As a safeguard, leave the first 8 digits, and change the remaining numbers. This way, the IMEI number will show up to It's corresponding device and can be activated thereafter.