So this issue, made me consult an ex consular officer, even if you have changed field it is still fine. The consular officer said so long that you show intent at interview that is what that matters. NIW is a long process, people can lose their jobs before interview, I saw on reddit when someone lost his job just 1 month before interview and he got the green card visa.
Telling people so long they are in their field they should be fine,
What happens to people who are not in their field of endeavor? It will create unnecessary anxiety to them.
I reviewed most NIW interviews here, there are a lot of people the consular officer didn't ask whether they are in their field of endeavor at interview.
Please If you are no longer in your field of endeavor, consult an attorney and ask how you can handle it.