USB Loader(s) have not been updated for the latest Nintendont rev.
Don't expect them to work hand in hand since most of the updates nowadays for all of them are mods not done by the creators.
Use the standalone app.
Yeah it's not a big deal not having loader support for wii u widescreen, I just wish the setting was remembered between launching games from a loader so I would only have to change it when switching from a widescreen to 4:3 game and vice versa. I might try looking into patching nintendont myself to have it default to whats stored in nincfg.bin for any settings not specified by the loader but that might be beyond my programming abilities.