This "scandal" seems like a nothingburger to me - Greenfield's campaign is just simplifying her biography to make it more streamlined; "I am a small businesswoman" gets straight to the aspect of the candidate that they want you to remember than "I worked at X company for a while, rose up, then worked at Y company".
Does it take away attention from voters bothering to look up her records at those companies? Possibly, but I think diverting attention away from any potential negatives about a candidate is the natural action from any campaign.
...and looking into this further, it seems that this really is a nothingburger:
This local news article concludes that what Ernst was attacking Greenfield for was normal business for a real estate company. It's just spun in the most negative light; again, normal stuff to do when attacking your opposition.