WC - interesting question (or at least, more interesting than what I'm meant to be doing). The Motorways Traffic (Scotland) Regulations 1995 don't mention "learners". It states that the holder of a provisional licence cannot drive on a motorway. While you have passed a test to drive a car, your motorbike entitlements are "provisional", as you have not passed the required motorcycle tests. I think anyway - as always, happy to be corrected.
I had no idea motorcyclist licensing was so complicated: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/369984/routes-to-your-motorcycle-licence.pdf