Of the major cloud families, the "cumulus" type (including stratocumulus, altocumulus and so on) are generally formed by convection in unstable air, leading to their "lumpy" or "heap-like" forms. The Stratus clouds, form in stable air, by advection (a layer of stratus or altostratus in advance of a warm front), or direct radiative cooling (fog). The absence of convection results in their layered form.
Altocumulus lenticularis does not seem to fit this pattern. It develops in stable air, that is being forced to rise perhaps as a result of upwind topography. Unlike other cumulus clouds, the flow of air remains laminar and not turbulent. There is no convection within the cloud, and the only reason that an extended layer of cloud doesn't form is that downwind the air descends, again as a result of the landforms. Lenticularis clouds are known to remain in one place and not move with the wind.
Lenticular clouds are often similar to cap clouds and pileus, which are classified as stratiform clouds.
So, is convection a defining factor for clouds to be classified as "cumulus" or "Altocumulus"? Is the classification of Lenticularis clouds as a species of Altocumulus based mainly on historical precedent, rather than consideration of their mode of formation?