From page 147 of the Owner's Manual--one would expect a more prominent warning! See attache image.

A - Suitable charging adapter
B - Unsuitable charging adapter
Using charging adapter for 12 volt socket/cigarette lighter
Risk of damage to the electrical system.

Only use a suitable charging adapter (A) that meets the following requirements:
The distance 1 between the ground connection and the upper edge of the charging adapter must be less than approx. 0.63 in. (16 mm).

Unsuitable charging adapters (B) with a larger distance 1 than 0.63 in. (16 mm) between the ground connection and the upper edge can destroy the sockets.

 

Good to know. I doubt I would've realized this if you hadn't posted it.

 

I saw that a while ago and I'm trying to work out exactly what the issue is with the longer connectors given that the offending measurement is between the ground connector and the seemingly arbitrary top of the connector, and the only thing I can come up with is that having more connector protrusion from the top of the socket would allow you to get a firmer grip on it and therefore yank it out with more force than would be possible with something where you have to use a couple fingers to gently work it out, so maybe Porsche is worried that in the former case you might yank the socket itself out along with the connector. My portable air compressor has a long connector and I'm always careful removing it by placing two fingers on the edge of the socket around the connector before pulling the connector itself out for this exact reason. I suspect that those who do the same will have no problem using such accessories with Porsche sockets.