Those products are almost always sourced from Chinese ODMs. They're the adults in the projects to the eyes of chip vendors, and the ODMs handle the quadrillion MOQ situation between them and vendors. Also products in [3] and [4] don't seem to support cellular? [3] smells AllWinner or MediaTek, [4] specifies TI OMAP in specifications page. Those are less NDA/bajilion MOQ bound.