Unfortunately you're another "victim" of the USB 3.0/USB 3.1 "switcheroo", as I'll explain.
The Kingston USB flash drive you purchased is the Data Traveler 100 G3 model. For all practical purposes it's a USB 3.0 model.
I can see the heading on the website refers to the flash drive as "USB 3.1 Gen 1 (USB 3.0)" and apparently you either failed to notice the USB 3.0 designation or the vendor from whom you purchased this item referred to it simply as a "USB 3.1" device.
The new USB speed naming conventions as promulgated by the industry association is a study in misrepresentation & confusion. It’s an absolute disgrace for consumers, since because of this new USB naming convention most of these consumers will have no idea that there can be no difference whatsoever re speed between a device advertised as USB 3.0 and another device advertised as USB 3.1.
USB 3.0 speed is 5 Gbps.
The new designations for USB devices (as promulgated by the USB Implementers Forum) are...
USB 3.1 Gen 1 and USB 3.1 Gen 2
USB 3.1 Gen 1 speed is 5 Gbps - NOTE IT IS THE IDENTICAL SPEED FOR WHAT WE HAVE TRADITIONALLY TERMED USB 3.0
Supposedly manufacturers are encouraged to use the designation "SuperSpeed USB" for these 5 Gbps devices.
USB 3.1 Gen 2 speed is 10 Gbps
Supposedly manufacturers are encouraged to use the designation "SuperSpeed USB 10 Gbps" for these devices.
So when you see a USB device (flash drive, etc.) advertised as "USB 3.1" it's a virtual certainty that device is what we formerly called a USB 3.0 flash drive. Only when it's specifically designated as a "USB 3.1 Gen 2" device can you be sure it's what we would ordinarily call a USB 3.1 device.
Now in Kingston's defense (at least with respect to the website you referred us to), it was indicated that your flash drive was a "USB 3.1 Gen 1 (USB 3.0)" device. From what I've seen that's more than most of the advertisements for "USB 3.1" devices have shown. At least there was a reference to "USB 3.0".