That is not the behavior I see. When I schedule a local notification with UNCalendarNotificationTrigger and only specify the hour and minute in the date component it still locks to an absolute time based on the timezone when scheduled. For example, I set the phone's timezone to PST and schedule a local notification to fire at 9:00 AM - the date component only sets hours and minutes. When I change the phone's timezone to MST, the notification will not fire at 9:00 AM MST and instead will fire at 10:00 AM MST (which is 9am PST). Afaik, there is no way to schedule a local notification to always fire at 9:00 AM regardless of timezone without extra coding to detect a timezone change and update the scheduled local notifications.
Topic:
App & System Services
SubTopic:
Notifications