If your question is directed at me and for the issues we are discussing here, no upload needed. I am using this app simply to find out what version of FW a particular device has. I have never used it to update FW
I believe that is what you will have to do. I seem to remember that the firmware updater only uploads one file at a time, and never a ZIP. I have never used this particular Leviton device, nor have I tried to update one, so you are on your own from there.
It does not involve using the Device Firmware Updater. The download via the link you provided above contains the files needed to update. The actuall update instruction are here
Thanks for the replies guys, and especially the super useful link @cdikland, thanks.
But it is disappointing that I need that special USB stick and can't use the hub
Consider it as a part of doing home automation "business" I have used it for FW updates, removing ghost zwave devices and including devices that under normal inclusion created havoc (i.e. Zooz 4-in-1 (ZSE40), C7, S0 - #7 by bill.d)