Its only O2 UK users that would have a problem, since we have CSC files and H4 firmware for the other main regions. H4 was released in every region through NPS
afaik. So you could always use Odin to go back to H4 with your region CSC and how would they know!
Anyway as soon as we get a single update for O2 uk, those users will be covered too. I personally don't think samsung care if you update or not, but are letting people know if all of a sudden lots of devices become bricked because of some dodgy un-official update, they might just refuse to waranty repair them.