What does world tech level actually mean? For an uncontacted world, TL is a little more obvious, it is the maximum technology that the world can produce and is in use on that world. A TL6 world has TL6-equipped soldiers, travel around the planet is likely conducted at TL6 levels and so on. 

For a contacted world it is less clear. A world might only have the ability to manufacture TL6 equipment but is there any particular reason they wouldn't be importing TL15 weapons and grav vehicles and so on? Much like Afghanistan on today's earth might only be able to manufacture TL3 or so, but they have cellphones and satellite phones, pickup trucks and what not. 

The worlds described in The Traveller Adventure are great - they have a better feeling of more real places to me - but clearly they are integrated into the imperium trading network and I don't understand why the soldiers on Aramanx are described as "equipped to TL6 levels" - why not equip soldiers with imported weapons and equipment?