esxi 6 & usb 3 hdd

As you can see from the command output below, my esxi server detects two usb disks. The western digital is usb2 and the verbatim a usb3.

[root@esxi:~] lsusb
Bus 002 Device 004: ID 18a5:0237 Verbatim, Ltd Portable Harddrive (500 GB)
Bus 002 Device 003: ID 1058:070a Western Digital Technologies, Inc. My Passport Essential SE, My Passport for Mac (WDBAAB)

Yet when I try to attach these disks on a virtual machine, only one of them appears. (you can ignore the broadcom)

Any ideas why?

Thanks