That‘s lame, unless perhaps you‘re in the regs. There is no need for ID discs in a reserve BMQ course, except that it‘s another piece of kit to be inspected.
Thankfully, I don‘t have them yet, since I still haven‘t discovered what my blood type is (nor do any doctors or clinics seem to be interested in taking my blood and telling me, unless of course I volunteer to give blood, which I haven‘t).
That said, I do have the temporary ID card, and I carry it any time I am in uniform or on army time.