Two land masses, not one
Malaysia is split by six hundred miles of sea. The peninsula is Kuala Lumpur, Penang and Langkawi; Borneo is Sabah and Sarawak, Kota Kinabalu, Kuching and the national parks. They are a domestic flight apart and they are not the same country to travel in. Coverage follows that split, thinning out as you move away from the Borneo towns and into the forest, which is worth knowing before you book a trip built around Kinabalu or the Kinabatangan.