Update from K10U to K15S Impossible?

MKP91

Hello..
I'm looking to get Komplete 15 Standard.
I own Komplete 10 Ultimate but when I try to buy the 15 Standard update it just says ''You won't be able to activate this product'' ..

So that made me think it's impossible to upgrade from Ultimate to Standard.. I'm not looking for all the stuff in the bigger version so Standard is perfect for me..
The price difference is insane though.. 199 euros for the update and 499 for the upgrade which NI seems to want me to buy..
Is this really the case that you can't update from 10 Ultimate to 15 Standard?

Best regards