White outline set to overprint

Hi!
I would like to consult one issue with people who have experience with DTP in the US market. I work as a DTP operator in a European company, and I have quite a lot of experience in preparing materials for printing. Recently, however, I have been starting to serve clients from the US market. All processes seem to be the same, and the target market of the product should not matter when it comes to prepress procedures. Meanwhile, from one of the clients, I received labels in which some texts have a white outline with the overprint option turned on. I'm used to the fact that in offset printing, white elements should always be knocked-out. I don't really see what's the point of giving an object an outline and then using the overprint option to make it invisible. The layout designer insists that it should be left that way. Is there any reasonable explanation why my client uses this procedure?