You can have it either way but not both ways. If an online meeting is set for 8:30am Sydney time, it's set for 10:30am New Zealand time, so Bixby can either be correct with that or ... if you set a meeting for 8:30 AM because you'll be in Sidney that day and the meeting is set for 8:30 AM, it will be st for 8:30 AM as seen by your phone in Sidney - when you're there and it's 10:30 in new Zealand.
There's not enough "smart" in "smartphone" to figure out which one you want. (Maybe we need a "figure timezone difference" checkbox in calendar apps, so you can tell it whether the appointment is for 8:30 AM on the phone or 8:30 at the place it's being set, but there wouldn't be very many customers asking for that, and they'd rather spend the time and effort on something that appeals to most customers, like dark mode or a new exciting background color for the calendar.)