The 'nofstab' cheat code prevents the Knoppix bootup (the linuxrc script) from scanning the local drives and creating an appropriate fstab. Inserting a USB device and fstab being edited is less dependent on Knoppix itself & more dependedent on how hotplug scripts and automount are configured. Will hotplug & automount force a rebuild? perhaps it will & I don't think that 'nofstab' will prevent that.
I hope this helps.
James