Dependents should be careful in using EAD while 485 pending

I know a case:

the chief applicant got his green card, while his wife, who is the dependent, was held in the process. The reason is that she used EAD to work while her I-485 pending. Immigration officer though that she belongs to EB3 although her hu*****and is EB1. She was told that she had to wait till her 485 becomes current!. Weired, isn't it?

Xiaobaitu, please explain a little bit about this issue. Thanks