Do these phantom outlines represent a problem with my imported objects?

Inkubo

I'm a wannabe PA trying to learn how to create architecture in Blender for use in DAZ Studio. Today instead of asking questions about how textures work and what the "units" are for horizontal and vertical tiles, I decided to make my own test-pattern texture and apply it to imported items. But I found something odd, and I'm not sure if it represents a no-nevermind situation, a bug in DS, or a problem with my imported objects.

When I right-click on an item with the Surface Selection tool and choose one of the "Select All..." options offered by the pop-up menu, the selection outline that appears encompasses my objects, but there are also some phantom outlines of the same objects, rotated by 90 degrees. You can see it as a pink outline in the attached screenshot. (I changed my accent color to a bright pink that stands out because it's unlikely to appear in any scene I might make.)

These objects were created in Blender, with units set to "feet," then UV mapped and unwrapped and exported with the following options: -Z Forward, Y Up, Apply Modifiers, Include Edges, Write Normals, Include UVs, Write Materials, Objects as OBJ Objects, Scale 1.0, and Path Mode Auto.

I imported them into DAZ Studio with the following options: Scale 3048%, no converted axes, Read UV Coordinates, Read Groups, Read Surfaces, and Read Materials Library. Then I applied the Iray Uber Base to all of them and chose my test-pattern image as the Base Color.