just tried to install 6.7 & then 7.2 (via Ventoy) to an USB stick, could not resize USB fat32 partition
does sparky not include msdos vfat fat32 support when booting from Ventoy?
or missing from ISO build?
I use Etcher and have never had a problem with a fat32 formatted USB drive to write Sparky or any Linux OS to it.
Are you using Linux or Windows to write the OS to the USB drive?
Also why are you trying to resize the partition? That should get done automatically.