I can tell you why they call them parade.
Because they are colourful and look fragile.
If all the shields made of straw, wood or leather were parade shields, we won't have a lot of battle shields...
The straw does the job, it will minimize the impact. Actualy it's the opposite the fancy full steel Persian and Indian shields were the parade shields.
For the colour it's the same, our world is grey, the past was colourful.
Plus I doubt that all the Ottoman shields captured during the siege of Vienna were parade shields.