Question regarding shared devices & group chat

Okay, so, a bit of a story here to help set up my question:

I recently changed jobs and had to turn in my old work phone. I did a factory reset on the phone, but I forgot to leave group chats that I was a part of before doing so. I have since made a new WhatsApp account and got re-added to one of my previous group chats. My old account was of course still listed as a member of the chat group. (It was listed simply as the phone NUMBER and no name)

Just today I have noticed that the NUMBER has since changed to a NAME, the name of which I can only assume is a the new employee that my previous employer handed the phone over to. I asked the group admin to remove them from the group chat. The group admin says that they did it (they also removed and re-added my new number/account for good measure).

Here comes the actual problem: From my perspective I can still see my PREVIOUS account as a member of the chat under the new name, but from the ADMIN's perspective they no longer see my old account, aka everything looks good.

What exactly is going on here? Can the person using my old phone see our chat? Is it just a display bug of some kind from my end only? Googling hasn't turned up anything for this issue.

Thanks,

-Ben