Yep, the Kahala Hilton was given a unique exemption from the rule, and was allowed to be operated by Hilton International and later Vista International under the Hilton name within the US, because it had been established under that name. I've always wondered how it came to be with Hilton International when the two chains were severed. The Kahala Hilton opened in January 1964, and the two chains were formally divided by Hilton in December 1964, but Hilton owned Hilton International until 1967, when they sold it to TWA.

I could be wrong, but I think the first Vista International Hotel may have been the one in New York, which opened in 1981, directly between the two towers of the WTC. It later became a Marriott and was destroyed on 9/11. 1981 sounds about right for when the Kahala moved from being marketed as part of Hilton International to Vista International.

The Hilton Hawaiian Village, however, was always a Hilton property, it was never part of Hilton International.

I'm only guessing, of course, but it's possible that the contracts for the Kahala Hilton were signed before Hawaii became a state in 1959, while the Hawaiian Village was bought from Kaiser in 1961. Thus, the Kahala may have contractually joined Hilton when it was located outside the 48 states, but the Hawaiian Village would have joined Hilton when it was within the 50 states.