Killed app relaunches same Activity instead of default Activity

Scenario:
Activity A has the LAUNCHER/DEFAULT stuff
Activity B also exists

- Launch app, A is shown
- Click on a button that causes B to show
- Click on a button that causes ProcessPhoenix to be invoked

I would expect the app to relaunch with only A showing, but B is relaunched instead. I tried specifying the Intent for A but even that doesn't work. Testing on an Emulator, API 28. Am I doing something wrong or is this a bug? I've combed over the code and can't figure out why this is happening.

Reproduce the scenario on an API 28 emulator: launch Activity A, navigate to Activity B, then invoke ProcessPhoenix. Start by tracing the relaunch path and the supplied Intent, and compare the observed task state with the expected result. Done means the process restarts with only Activity A showing.

Written by the indexing model from the issue text.