Yes, I use it the power wire into it as a switched live. The USB is naturally 12V in - 5V out. Personally, I could not get on with the underseat USB to power my phone and added a second USB on the handlebars.
I just added an extension lead....pokes out near the seat....tucks in when not in use....I hate cluttered handle bars.....but that just me.
Traveler, didn't know that there is a USB under the tank; is this one in addition to the one under the seat???
Nickjaxe - did the same; got a 3.3 foot usb to C extension cable from Amazon. That length gets the end close enough to your saddle bags to charge a cell in the bag; coils nice under the seat if no bags; see the item here: https://www.amazon.com/dp/B086DPMFLL?ref=ppx_yo2ov_dt_b_product_details&th=1 Also got some dust covers for the C end from Amazon.