this is true.
If you make a "clean" first install, it will save to the dol's folder.
the loader doesn't have a hardcoded path, it's using "current partition":\apps\usbloader_gx\
if you want to "force" the setting to USB, delete from SD, remove SD, launch the loader to create it on USB.
next time you launch with SD inserted, it will scan all found partitions to load the settings.
SD > USB partition 1 > USB partition 2 > ... > USB partition 8
if you already had a setting file on SD and move the loader to usb, it will use SD setting file in priority even if you have another one on USB. So be sure to delete the setting file on SD and it will create it again on USB.
Or if you don't want to lose your current settings, edit the GXconfig.ini file on your computer to replace "sd" with "usb1" for USB first partition, "usb2" for usb second partition, etc.
or edit all path directly in the loader's settings one by one but it's faster on computer or to delete it and recreated it.
Personally, I recommend using SD card to prevent issues (in case you use dual port feature).
if you use only one port, then full usb is fine.