For new test cases, how to stop the Tester field automatically defaulting to the name of whoever created the card?

On creating a new test case in Azure DevOps, we've noticed the 'Tester' field is automatically set to the name of whoever created the card. This is incorrect, as testing on the card has not started and none of the QA team has picked it up yet. I imagine very few software companies have just one tester and instead have multiple people working through test suites once testing begins. So I imagine this must be an issue for other teams. How can the field be changed to show that no testers have yet been assigned and the test case is waiting to be picked up by one of the team?

n.b There doesn't appear to be any assigned rules at present, so nothing that I can go in and modify to stop automatically adding a name. And there is nowhere to edit the 'Tester' field. Even if you create a new template, when you try to edit that template the 'Tester' field still doesn't show up.

Tried asking this on Super User. Was advised to re-ask the question here.