Doesn't Australia do the same thing? I tried to read the rules for Australians, I didn't understand it all , but looks to be a mess also. Just did a google search and I got this?
UK pensioners in other countries – most notably Australia, Canada, New Zealand and South Africa – have their pension frozen i.e. paid at the same rate as it was when they first became entitled, or the date they left the UK if they were already pensioners then.