Every big company has differing internal requirements for protective clothing, including style of stripes and colour schemes. Some differ by site, while others have national standards. For contractors it is even more variable.
The HiVis reflective striping on cotton with full length sleeves and trousers has often been supplied as suitable for all circumstances. IE summer, winter, day or night. That saves on extra employer costs if they were to provide more than one style.
Some will suggest the one solution suits all is a poor compromise. I agree. Outdoor daytime work, mid summer inland Aust etc, light and breathable is the way to go. The stripes block the cloth from breathing, and do collect heat while blocking cooling. For those over the shoulder designed stripes, there is also a noticeable reflection onto the face and neck, of indeterminate radiation.
Personal observation is that as a minimum the striping can become too hot to touch from the effects of the sun. The stripes also cause additional sweating and hot spots on the skin. Adding a layer underneath may be a poor solution for a hot environment. Although there is also the type of material used with the striping to consider. It is typically not an open light weave but heavy cotton drill, which may also be a poor choice in hot outdoor environments.