Activity experience is tied to user's login/profile cookies - is this expected?

My QA team sometimes sees the below scenario, on both website and apps:

1) Open website or app

2) Logs into loyalty account

3) Enter a test and observe which experience they are placed into (let's say Exp A here)

4) Leaves site/app and clears cookies or deletes & reinstalls app

5) Opens website or app again

6) Enters test and is placed into Exp B

7) Logs into same loyalty account

😎 Upon logging in, they are switched back to Exp A

This happens somewhat frequently, especially on website tests. However, we've noticed that it does not happen consistently, sometimes they log in and the experience does not revert back to the one they original qualified for when logging in. Which one is the expected behavior?