WHY? Spiral Car Truck Antenna

I was in the market for a new car antenna and noticed these new spiral antennas. I know a 31 inch antenna is 1/4 wave length for 100mhz FM. What is this extra spiral for? I did some research, its for wind resistance and noise. Shorty antennas usually have an internal spiral or something that leads to a 1/4 wave length 31 inches inside.

Antenna in this video
https://www.amazon.com/gp/product/B0049MV3BU/ref=as_li_tl?ie=UTF8&tag=fintechcomm0f-20&camp=1789&creative=9325&linkCode=as2&creativeASIN=B0049MV3BU&linkId=391e14ecc20a231915d6d1f435094bcc