They are left off because they are already planned for release or in the case of Rifleman III it is already done and waiting to be released.
Rattler MKII Anti-Aerospace Mobile Fortress (Map scale version)Cenurion Mech Scale FighterPlease
Rattler MKII Anti-Aerospace Mobile Fortress (Map scale version)
If the dimensions are 3 hexes by 3 hexes, what would that look like on a hex map? Circle of 7? It would definitely make for an interesting scenario objective.