I am not quite sure what you mean by WordPress edit UI also does not hide end time?
When editing an event (in the block editor) if you have “Hide End Time” enabled, the end date/time is indeed greyed out.
But when you’re on the Events tab in the admin screen (which shows the list of events to edit), the end date/time is shown, and its set to 11:50PM. Theres nothing to indicate that end date/time is not set/shown. Thats confusing.
ie: wp-admin/edit.php?post_type=ajde_events