TC will not mount a disk unless there's a TC installation there, e.g. a /tce directory, or if you told it to. This is to support persistence when booting from a CD, for example.
It sounds like you have a TC install on your disk, and extensions get loop-mounted. The "base norestore" bootcodes are intended for operating in RAM, to for example fix an installation. But any USB stick made properly should have bootcodes referring to the stick's tce directory, did you by chance use a third-party installer to make those USB sticks?