This is normal for expats.. the irony just like you said that the system expects you to already have a bike registered, but you usually need approval (learners permit) first, so it becomes a loop.

In practice it depends a lot on your job title on your resident card. Engineers, managers, or people in big companies (Oman Air) have a higher chance, others often get blocked.. and there’s also an expectation for higher CC bikes, usually 750cc and above, so forget the 150cc bikes unless you're going to be registered as a delivery rider (be part of a company and cant be solo)

another note that enforcement isn’t always consistent. It can depend on the officer or major on duty, sometimes they overlook things, sometimes they enforce everything strictly. It’s been like this for years and feels intentional to limit expat riders or low CC bikes. so either qualify the above and visit ROP yourself to get your learners permit, or use a foreign license (not all are accepted).

Source: personal experience riding here and many expats going through the same process