Icons, buttons, and other graphical elements are pulled out of the specific template file (TPName.vtt) for each interface. if the icon sizes are different for design or realestate reasons then the designer/programmer needs to resize/create new for those templates. A design choice,miscommunication between developer/designers, poor or lack of specification by the project manager, or a simple clerical error, can explain the difference in icons.

Unless they have better tools than those provided in pro-e, working with themes can be flakey (pro-e crashes) and it is easy to make a mistake.