IssueTracker

Component used: Navigation
Version used:2.0.0
Devices/Android versions reproduced on:Emulator 8.0, Pixel 2 XL 9.x

So basically for reproduce you need simple flow:
1. Graph with Fragment with arguments with default values as default destination
2. Main Activity launcher which hosts the graph
3. in Activity.onCreate()  start listen for destination changes:
navController.addOnDestinationChangedListener { controller, destination, arguments -> }
4. When activity first creates onDestinationChanged() gets called but arguments is null.

Fragment will receive those default arguments tho.
This happens only if fragment is startDestination. If we navigate to this fragment otherwise (clicks, menus) with NavController.navigate() default arguments will be at place.