Everywhere else MeshID, TextureID, and xID exist on ROBLOX, the the D in ID is lowercase.
MeshPart: MeshID & TextureID
SpecialMesh: MeshId & TextureId
MeshPart properties should be MeshId & TextureId and not MeshID and TextureID with uppercase 'D’s. If not for the sake of global consistency, for the sake of being consistent with SpecialMeshes which are supposed to be able to be seamlessly swapped out with MeshParts. The current properties should be deprecated and consistent properties added in their stead.