No intention to offend. I chose the term "Oriental" rather than "Asian" since I saw an ethnic difference in people from this region from people from elsewhere in Asia, such as India.
The preferred term there would be East Asian.
They did indeed. But in the early seasons (I just finished a complete rewatch of the the series, one ep a week over the last 5 years!), it seemed that any MAIN story character was usually played by a non-Asian TV actor like the above-mentioned fellas. 2ndary parts were often Asian TV actors like Phiilp Ahn or James Hong. Background actors were often local Hawaiian talent. Naturally there were exceptions (female Asian parts were usually female Asians like Nancy Quan or France Nuyen). In later seasons it got better, but early on there were a lot of fake epicanthic folds on display!
That's not surprising. I suspected that would be the case, but I haven't seen the show since I was very young.