After combining that with your other post, perhaps the formula they are using is iCloud account on a 'difference' device where it calculates if the new device is 'better' than the old one, thus was a device upgrade and therefore you may want to try the arcade. Personally I don't care for the arcade, but it does seem to be some sort of one-off notification when something in your device/account mix changes.

Reminds me of the Office365 trial tile in Windows that doesn't actually do anything but when you open the start menu it is always there in accounts that are newly signed in to a computer. It's not really in the way, but it is always in your face until you remove it (but then it does stay away).