It's not?
The perks page clearly states that it's for Note 8, 10.1, home sync devices -- not phones. I'm well aware of the perks page since I also bought a Note 10.1 2014.
I guess someone found a loophole where they put in their Note2, 3, S3, S4 serial numbers and was able to get some of the perks (myself included!)
I'm sure Samsung pulled the perks registration page since they were getting an influx of phone registrations.
If you want to test my theory, the perks registration page is back up. Someone try registering a Samsung phone and see if it still gives you the perks credits.