My guess would be that many USB-C products are charging cables, dongles, and other items that the average user would not associate with having the capability to

My guess would be that many USB-C products are charging cables, dongles, and other items that the average user would not associate with having the capability to store data making them inherently "safe" in their eyes. USB-A, on the other hand, is commonly associated with storing data, and the majority of user awareness and education about the danger of unknown devices is focused on flash drives. For these reasons I can see how someone without technical experience may believe that flash drives specifically are potentially dangerous, while believing that other USB-A/USB-C cables/adapters/chargers are safe. In my experience most users don't even know what USB-B is