At check-in at the Hilton Auckland today I was given a letter with Diamond benefits and the wifi code on it.
When connecting to the wifi it gave the option of using a code or name/room number - so I decided to try both. Neither gave any indication of receiving Premium Internet (and no option to pay for it), but...
Using the wifi code :
Using the name/room login :
So fairly clearly the wifi code, even though it's on the Diamond welcome letter, is giving standard wifi, whilst the name/room number login is giving premium.