Although you can only buy the SanDisk 64GB Dual Drive USB-C Flash Drive from Apple Stores but because it comes pre-formatted as exFAT, it works just as well with USB Type-C based Thunderbolt 3 Windows PC's like the Spectre x360 (2nd Generation 2017).
Even though Thunderbolt 3 PC's like the Spectre x360 (2nd Generation 2017) support USB 3.1 Gen 2 (10 Gb/s) over USB Type-C, the SanDisk 64GB Dual Drive USB-C Flash Drive only supports USB 3.1 Gen 1 (5 Gb/s) link speeds which is good enough for most casual users.
However, when we connected the SanDisk 64GB Dual Drive USB-C Flash Drive to the Spectre x360 (2nd Generation 2017) over USB Type-C, we could clearly see the flash drive was having problems trying to connect to the Spectre x360 laptop.
The Spectre x360 screenshots below show the SanDisk 64GB Dual Drive USB-C Flash Drive not showing up properly in both Device Manager and Disk Management.
The flash drive briefly shows up in Device Manager as a Generic SD/MMC USB device and keeps on enumerating repeatedly after several refreshes.
Similarly in Disk Management, the SanDisk 64GB Dual Drive USB-C Flash Drive also constantly enumerates as an unrecognizable device.
Hence we can confirm that the SanDisk 64GB Dual Drive USB-C Flash Drive could not be used with the Spectre x360 (2nd Generation 2017) when connected over USB Type-C.
However, once we replace the SanDisk 64GB Dual Drive USB-C Flash Drive with the Kingston DataTraveler microDuo 3C over the same USB Type-C, we don't see any issue with the Kingston DataTraveler microDuo 3C connecting correctly to the Spectre x360 (2nd Generation 2017).