(NOT Suitable For Factory Halogen Taillights Version)

The short answer is that the reason why some manufacturers indicate that their after-market (meaning, non-OEM) tail-light fittings are not compatible with halogen built cars is NOT due to coding limitations. Fact is that ALL versions of the module that operates the 35 x exterior lights (i.e. central electrics module ) on MQB platform cars (like your mk7) are capable of operating both incandescent and LED lamps in tail-light fittings.

The longer answer is that the limitation has its principal cause in basic manufacturing economics - it's ostensibly because of the amount of copper that is factory installed into MQB platform cars with different tail-light options! To explain - look at the total number of lamps that are embedded in OEM incandescent tail-light fittings  compared to OEM LED tail-lights. The lamp-count is greater on LED tail-lights!!

So, on MQB platform cars, VAG (being VW/Audi) install a separate wire from the central electrics module to each individual lamp on tail-light fittings (with one exception). This means that on cars that are built with incandescent lamps - the wire-count in the tail-light cable-loom to the car rear is less than for those cars that are factory built with LED tail-lights (the underpinning reason for this practice being that it is financially beneficial for VAG to produce 2 x different wiring looms, thereby saving on the cost of copper).

However, some non-OEM manufacturers of after market LED tail-ights overcome the wire-count problem by adding an extra exterior "harness" into the retrofit installation. The purpose of the harness is to join-together lamps with the same lighting function on the tail-lights on both car-sides. For example, the harness joins together the 2 x brake-light lamps and separately, the harness joins together the 2 x Parking Lights lamps on either car side. Plus, the harness also joins together both the outer and inner turn-signal lamps on the new LED fittings. This "parallel" joining of lamps creates spare wires that can then be re-coded on the central electrics module to operate the additional lamps in the new LED fittings.

Bottom line = if you are considering retrofitting LED tail-lights that are designed for a halogen built Mk7, I suggest for compatibility reasons that source the harness from the same manufacturer (and the coding instructions). Again, these are non-OEM parts - better not to risk incompatibility problems!!

Hope this makes sense!!

Don